Some questions about bonds

I am learning more about the bonds and have some questions

1. Are Treasury zeros (STRIPS) same as US treasury and govt backed. Or they are something else? Are they insured?

2. I think Government-sponsored enterprises (GSEs) securities and Government Agencies bond are same thing?

3. Are GSEs insured?

4. Are municipal bonds insured?

5. I think CDs are also insured until $250K, even for foreign investors who don't live in the US.

6. Should I buy U.S. Treasuries or STRIPS or GSEs or CD or Municipal bonds if all of them are insured? Should I go with the highest yield blindly?

7. Somebody told me to look at YTM and maturity to decide which one is best deal. But why zeroes have less YTM than Treasuries even though they are the same thing?