LogFAQs > #929413956

No special rules for side chapters. You can do them if you want.

First win criteria is farthest chapter reached. So if hypothetically someone got their 5th game over in chapter 25 with 0 side chapters completed and someone else got their 5th game over in chapter 24 with all previous side chapters completed, the player who reached chapter 25 would win.

If the furthest chapter is a tie, (and they actually beat the game) then it's fewest game overs (less than 5). If that's a tie then most side chapters completed is the next tie break.