EDIT: I have made this post CW, so that other users can update it, if needed.
To answer my question (at least partially) I checked the lists of Gold medalists from junior and senior championships as shown at elitepropects here and here.
Note that the lists from older championships are incomplete. (I was able to find that also Makarov, Kasatonov, Krutov, Pervukhin have achieved this. They are not in the list on eliteprospects. I have added them to the list below. Just for reference, I will add here also the version of the lists I was working with - in case they will be updated later. Here are they: juniors and seniors.)
I found the following players with junior and senior medals from the same year:
Viacheslav Fetisov and Sergei Makarov in 1978,
Sergej Fedorov in 1989,
Jamie Storr in 1994,
Martin Havlát in 2000,
Jonathan Toews in 2007, Henri Jokiharju and Kaapo Kakko in 2019.
One player won the gold from senior championship one year sooner than junior gold:
Patrice Bergeron (2005 and 2004).
Players
Here is the list of players who won both junior and senior medal on WC, ordered by the year when they won the junior gold medal (for the first time).
- Zinetula Bilyaletdinov won junior gold medal in 1974 and 6 senior gold medals in 1978, 1979, 1981-1983 and 1986. (Additionally he won gold medal as a coach in 2012.) It is worth mentioning that the first three WJC tournaments (1974-1976) are considered unofficial.
- Viacheslav Fetisov won three junior gold medals (1976-1978) and seven senior golds (1978, 1981-1983, 1986, 1989, 1990).
- Vasili Pervukhin won junior gold in 1976 and 6 senior golds (1978, 1979, 1981-1983 and 1986).
- Sergei Makarov won two junior gold medals (1977 and 1978) and 8 senior gold medals (1978, 1979, 1981-1983, 1986, 1989, 1990).
- Alexei Kasatonov won two junior gold medals (1978 and 1979) and 5 senior gold medals (1981-1983, 1986, 1989, 1990).
- Vladimir Krutov won two junior gold medals in 1979 and 1980 and 5 senior gold medalls (1981-1983, 1986, 1989).
- Igor Larionov won two junior gold medals (1979, 1980) and 4 senior gold medals (1982-1983, 1986, 1989). (He is also a member of Triple Gold Club, having won Olympic Games, World Championship and the Stanley Cup. Igor Larionov and Peter Forsberg are the only players to have won each of these three competitionsps more than once.)
- Peter Andersson won junior gold medal in 1981 and 2 senior gold medals in 1987 and 1991.
- Peter Åslin won junior gold medal in 1981 and senior gold medal in 1992.
- Peter Sundström won junior gold medal in 1981 and senior gold medal in 1987
- Ilya Byakin won junior gold medal in 1983 and 3 senior gold medals in 1989, 1990 and 1993.
- Yuri Khmylev won junior gold medal in 1984 and 1986 and 2 senior gold medals in 1986 and 1989.
- Evgeny Davydov won junior gold medal in 1986 and senior gold medal in 1990.
- Janne Ojanen won junior gold medal in 1987 and senior gold medal in 1995.
- Joe Sakic won junior gold medal in 1988 and senior gold medal in 1994. He is also a member of Triple Gold Club.
- Mark Recchi won junior gold medal in 1988 and senior gold medals in 1997.
- Sergej Fedorov won junior gold medal in 1989 and 3 senior gold medals in 1989, 1990 and 2008.
- Pavel Bure won junior gold medal in 1989 and senior gold medal in 1990.
- Dmitri Yushkevich won junior gold medal in 1989 and senior gold medal in 1993.
- Kris Draper won two junior gold medals (1990, 1991) and one senior gold medal (2003).
- Mike Ricci won junior gold medal in 1990 and senior gold medal in 1994.
- Scott Niedermayer won junior gold medal in 1991 and senior gold medal in 2004. He is a member of Triple Gold Club.
- Alexei Yashin won junior gold medal in 1992 and senior gold medal in 1993.
- Joël Bouchard won two junior gold medals (1993, 1994) and one senior gold medal (1997).
- Chris Pronger won junior gold medal in 1993 and senior gold medal in 1997. He is a member of Triple Gold Club.
- Chris Gratton won junior gold medal in 1993 and senior gold medal in 1997.
- Paul Kariya won junior gold medal in 1993 and senior gold medal in 1994.
- Rob Niedermayer won junior gold medal in 1993 and senior gold medal in 2004.
- Anson Carter won junior gold medal in 1994 and two senior gold medals in 1997 and 2003.
- Jeff Friesen won two junior gold medals (1994, 1995) and two senior gold medals (1997, 2004).
- Bryan McCabe won two junior gold medals (1994, 1995) and one senior gold medal (1997).
- Jamie Storr won two junior gold medals (1994 and 1995) and one senior gold medal (1994).
- Shean Donovan won junior gold medal in 1995 and senior gold medal in 1997.
- Ryan Smyth won junior gold medal in 1995 and two senior gold medals (2003, 2004).
- Marc Denis won two junior gold medals (1996, 1997) and one senior gold medal (2004).
- Jarome Iginla won junior gold medal in 1996 and senior gold medal in 1997.
- Martin Biron won junior gold medal in 1997 and senior gold medal in 2003.
- Daniel Brière won junior gold medal in 1997 and two senior gold medals (2003, 2004).
- Niko Kapanen won junior gold medal in 1998 and senior gold medal in 2011.
- Pasi Puistola won junior gold medal in 1998 and senior gold medal in 2011.
- Maxim Afinogenov won junior gold medal in 1999 and senior gold medal in 2008.
- Vitali Vishnevski won junior gold medal in 1999 and senior gold medal in 2009.
- Martin Havlát won both junior and senior gold medal in 2000.
- Josef Vašíček won junior gold medal in 2000 and senior gold medal in 2005.
- Radim Vrbata won junior gold medal in 2001 and senior gold medal in 2005.
- Alexander Frolov won junior gold medal in 2002 and senior gold medal in 2009.
- Denis Grebeshkov won two junior (2002, 2003) and two senior (2008, 2009) gold medals.
- Alexander Perezhogin won two junior (2002, 2003) and two senior (2009, 2012) gold medals.
- Fedor Tyutin won two junior golds (2002, 2003). He won senior gold medal in 2008. Grebeshkov, Perezhogin and Tyutin also have gold medal from 2001 U18 Championship.
- Alexander Svitov von junior gold medal in 2002 and senior gold medal in 2012.
- Anton Volchenkov won junior gold medal in 2002 and senior gold medal in 2009.
- Konstantin Barulin won junior gold medal in 2003 and senior gold medal in 2012.
- Konstantin Korneyev won junior gold medal in 2003 and two senior gold medal in 2008 and 2009.
- Alexander Ovechkin won junior gold medal in 2003 and 3 senior gold medals (2008, 2012, 2014).
- Nikolai Zherdev won junior gold medal in 2003 and two senior gold medals in 2009 and 2012.
- Patrice Bergeron won junior gold medal in 2005 and senior gold medal in 2004. He is a member of Triple Gold Club.
- Corey Perry won junior gold medal in 2005 and senior gold medal in 2016. He also has two olympic gold medals from 2010 and 2014 and is a member of Triple Gold Club.
- Dion Phaneuf won junior gold medal in 2005 and senior gold medal in 2007.
- Shea Weber won junior gold medal in 2005 and senior gold medal in 2007.
- Jonathan Toews won two junior gold medals in 2006 and 2007. In 2007 he won also senior gold medal. He is a member of Triple Gold Club.
- Brad Marchand won two junior gold medals in 2007 and 2008. He won senior gold medal in 2016.
- Ryan Ellis won junior gold medal in 2008 and senior gold medal in 2016. He also has gold medal from 2008 U18 championship.
- Claude Giroux won junior gold medal in 2008 and senior gold medal in 2015.
- Jordan Eberle won junior gold medal in 2009 and senior gold medal in 2015. He has also a gold medal from 2008 U18 Championship.
- Tyler Ennis won junior gold medal in 2009 and senior gold medal in 2015.
- Evgeny Kuznetsov won junior gold medal in 2011 and two senior gold medals in 2012 and 2014.
- Sergei Kalinin won junior gold medal in 2011 and senior gold medal in 2014.
- Dmitri Orlov won junior gold medal in 2011 and senior gold medal in 2014.
- Petter Granberg and Johan Gustafsson won junior gold medal in 2012 and senior gold medal in 2013.
- Jonas Brodin, William Karlsson, Joakim Nordström and Victor Rask won junior gold medal in 2012 and senior gold medal in 2017.
- John Klingberg won junior gold medal in 2012 and two senior gold medal in 2017 and 2018.
- Filip Forsberg, Johan Larsson,
Rickard Rakell and Mika Zibanejad
won junior gold medal in 2012 and senior gold medal in 2018.
- Mikko Lehtonen won junior gold medal in 2014 and senior gold medals in 2019 and 2022. He also has an Olympic gold medal from 2022.
- Esa Lindell won junior gold medal in 2014 and senior gold medal in 2022.
- Saku Mäenalanen and Ville Pokka won junior gold medal in 2014 and senior gold medal in 2022. They also have an Olympic gold medal from 2022.
- Max Domi won junior gold medal in 2015 and senior gold medal in 2016.
- Ryan O'Reilly won junior gold medal in 2015 and senior gold medal in 2016.
- Sam Reinhart won junior gold medal in 2015 and senior gold medal in 2016. He also has gold medal from U18 championship in 2013.
- Connor McDavid won junior gold medal in 2015 and senior gold medal in 2016. He also has gold medal from U18 championship in 2013.
- Nick Paul won junior gold medal in 2015 and senior gold medal in 2021.
- Juho Lammikko won junior gold medal in 2016 and senior gold medals in 2019 and 2022.
- Niko Mikkola, Veini
Vehviläinen won junior gold medal in 2016 and senior gold medal in 2019.
- Max Comtois won junior gold medal in 2018 and senior gold medal in 2021.
- Henri Jokiharju won junior and senior gold medals in 2019. He also has gold medal from U18 championship in 2016.
- Kaapo Kakko won junior and senior gold medals in 2019. He also won gold medal from U18 championship in 2018.
- Jacob Bernard-Docker, Liam Foudy and Gabriel Vilardi won junior gold medal in 2020 and senior gold medal in 2021.
Coaches
There are also several coaches who lead both juniors and seniors to gold medal at World Championships.
