even if it doesn't help you with your rail tricks (i think it will) it's really fun and gives you a new skill and way to look at obstacles. Plus you can do it year round, unlike skiing, unless you live somewhere you can of course. And you don't have to get expensive skates, you can easily find cheap ones, quick, check rollerwarehouse or aggressivemall for black friday deals.
those inner wheels are called anti rockers. i would not get them, but get juice boxes instead. What they do is fill in the gap of the frame of where a wheel would be. so it gives the frame strength, and it wont crack when hitting rails overtime. and you dont want a cracked frame.
all preference. personally, i skate USD carbons with xsjado frames which only have spots for two outside wheels and the rest is groove. You could put anti rockers (little plastic wheels) or smaller wheels in the inner parts of a frame if you wanted. all preference.
only 50-50 frames get juice blocks. create original get g blocks and kizer get nothing of the sort since they have M types. I think normal frames lock better, but freestyle lets you fit easier n some stuff. plus you can pivot on rails which is fun for doing ski-like tricks. or at least i think so.