Timing Rules in Seven Wonders
1) Nothing to say for me here ;-)

2) I'm not sure about the actual rules, but I think the penalty of disallowing everything else would be too harsh, as the player loses a complete turn. One could argue if only the three coins should be allowed or building a part of the wonder as well. Personally, I would allow both.

3) Again, not 100% sure: as you cannot use coins that you got this turn, you shouldn't be able to use any resources that have become available in the same turn. My thinking is, everybody builds at the same time and hence completes their building at the same time, so you can't get anything out of another building to complete your own.