A batsman who is at 99 not out and at non-striker needs 1 run to win off the last ball. How is it possible that they win the game and also that the batsman reaches his century?
I think the only way to do it is by way of penalty runs. Most straightforwardly, the batsmen could try to steal a run during the bowler's run up. As soon as they cross, the umpires would call dead ball and award 5 penalty runs to the fielding side. The batsmen return to their original ends. Now the batting side needs 6 to win off one ball. The bowler could then bowl a no ball or a wide allowing the batsmen to cross, which would score 2 runs. Now the guy on 99 is on strike with one legal ball to go and needing 4 to win.
The batsman attempt another run before the final ball is bowled (once bowler has commenced his run up), cross, and the other batsman gets run out.
The batsman who is on 99 is now on strike and hits a single off the one remaining delivery.
When the batsman going for a run , one of the either is obstructed by a fielder in which a run is not completed...in this case the umpire will call dead ball and the non striker who is on 99 will take strike...( as the batsman has crossed each other)
There are two other cases that haven't been raised here - either a no ball or wide being bowled. In both cases the ball is rebowled and the batsman are able to run a single (or three for that matter).