No games have 4.2 on them, not a single one.
Your Black screen issue is not neccessarily a IOS issue, these errors are freezes on black screen with no message.
1. Not unless you go messing with System IOS 30/50/60/70
2. Better to use IOS from NUSD, then disc, then IOSpatcher. Patching works just for 1 game, the next game will need it and then next aso.
3. No, Yes,
4. The error is probably something else. Does it give a number?