1. There's really no way to avoid it, haha. The only way to keep a Beyblade looking new is to avoid using it at all
2. Eh, not really. A mint Wyvang Attacker can hurt a bit if you grab it at the wrong angle, but for the most part MFB Beyblades are harmless (not too sure about plastics/HMS, should ask someone else about that).
3. There isn't really an answer to this question. There are so many different combos that use right and left rotation, and the "web" of what beats/loses to what is so insanely intricate, that TBH giving an answer for "which one is better" between competitive customs is rarely a simple thing, and almost never clear-cut (not just in this case).
In a nutshell, no, not necessarily. Left rotation doesn't automatically make a Beyblade better. It's definitely an applicable tool, but you've gotta use it right, and even then, depending on your opponent it might not work to your advantage at all.