Has a play-in team (a team that entered the tournament bracket through the preliminary "First Four" tournament games) ever won the NCAA Men's Basketball Championship? If not, what are the lowest seeded teams to win?
Has a play-in team ever won the NCAA Men's Basketball Championship?
If not, what [is] the lowest seeded [team] to win?
Villanova is credited as being the lowest-seed to win the NCAA Men's Basketball Championship as an 8 seed in 1985(1).
The NCAA tournament expanded to include the play-in teams starting in 2011. Since 2011 tournament the lowest seed to win it all has been a 7 seed (UCONN). To answer the first part of your question, no play-in team has even made it to the championship let alone won it.
To answer your second part, "Three 11 seeds have made it to the round of four--LSU in 1986, George Mason in 2006 and VCU in 2011. Throughout the history of the tournament, just 14 teams seeded seventh or worse have made it to the Final Four. The lowest seed to win the tournament and national title was the No. 8 seeded Villanova in 1985" Source:LINK HERE