Ok, so here we go:
1. It isn't possible, cause you don't need it (cars are always 100%)
2. The treasure hunt event isn't possible, cause you don't need it (you have always enough money and you can buy almost every item in the store).
3. This is really a bug, but it will be fixed in some time, I think.
4. That's right. I don't know if there is a solution for that.
5. That's also right, I have the same problem, but maybe it will be fixed.
6. I don't know about that. I can't help fot that.
7. The car price packs, etc. won't be available to buy, cause it's too stressful to program it and you don't need them (you have almost every car in store and you can also create special editions).
Hope this helps so far. :)