1. No, all your T/SQL will work just the same.
2. It’ll work just fine.
3. Yes you can restore a database between x64 and x32.
As long as you aren’t using SQL Mail, or DTS then you should be fine. If you are using SSIS then you’ll need to be careful with your SSIS packages, and there is some difference in how SQL setups up it’s procedure cache between x32 and x64.