2. What materials are acceptable? Is it OK to use galvanized pipe?
(My contractor is doing that and I am afraid of future gas leaks due
to rust.) What does the code say.


Here is whats required in Arizona..

Gas yard line must be scotch (green)coated for burial in the ground or
approved plastic with a minimum 18 AWG copper tracer wire.

We bought our ScotchCoated pipe at Naughtons.