yes
yes if using salted butter do not add salt
If a frosting recipe has butter in it, use the butter. Oil will change the consistency and not taste good.
You could use oil, or butter. I would use margarine because butter is full of fat and some brands of butter are unhealthy.
Real butter can be used instead of imitation butter flavoring. Imitation butter flavoring is typically used instead of real butter when people have health issues that make the consumption of butter bad for them.
Yes, just put a tiny amount of salt in if you use regular.
No.
yes
No.
Butter/margarine.
Use the same amount of butter.
Margarine can be used as a substitute for the butter.