No, you don't need a spinner but as some have said it's a bit easier if you use an electric starter although my ST45 is very easy to hand start (that's with zero nitro fuel too ). One thing to watch for though if you don't use a spinner is that the CG doesn't move back too far.

AMA rules regarding spinner nuts etc don't apply to us in Australia unless local club rules cover things like that although I've never heard of any club doing that.