To clarify:
1. Can it be any Class A car, regardless of whether it's from a car pack or not? (I honestly can't figure out which are base game cars and which are from car packs

)
2. Can the car be tuned and upgraded, (so long as it says in class of course) or does it have to be stock?
3. Can I update my lap time if I improve on it after I post my screenshot?
To ask:
4. I can't find an indicator for the HUD to show me where/when I go wrong and "dirty" a lap. Is it a thing of Forza 4 history? If I turn on Rewind and watch for the "Rewind" prompt will this amount to the same thing? And will activating Rewind but not actually using it still "dirty" a lap?