Ok I have to cupcakes in bugs theme and have to pipe grass on the cupcake. My question is can I do with bettercream or do I HAVE to use regular buttercream??

Please advice!

Yes you can. Just don't overwhip it or it will be impossible to pipe.

You can, but keep in mind if you are coloring it you won'y get a dark green. You can only get pastel colors with Beterceme.