Here are my questions;
1.I have read the galvanizing flakes off of the inside of the pipes when exposed to natural gas. Do I need to put a dirt trap pocket/drip leg in the line at the grill?
Most gas supplies these days do not have that reaction any longer.
2.I have read there is electrolysis between brass and galvanized pipe so the pipe will corrode away eventually. Is this true and if so how do I avoid it?
ELectrolysis is only a factor when there is there is a reragent, such as water, creating the current. It is not a factor with gas, and because of the positions of steel and brass on the nobility scale, it does not occur between them anyway.
3.Will I have electrolysis between black iron and galvanized pipe?
They are the same material, so even if gas caused electrolsis it would not occur.
4.I live in Baltimore County, Maryland. Can I use the black iron pipe outside and paint it to protect it?
5. If I can use the black pipe outside should I still use a drip leg at the grill?
The drip leg is not a "galvanized pipe" requirement. It is also to contain moisture and "dirt" from the gas, so if you buiding department requires them you should install it.