Depends on software your phone is running now.
-For 2.3.4 there is no current method of rooting yet..
-For 2.3.3 here's a link to guide you: [how-to] root: Gingerbread 2.3.3 - Android Forums
-As for ROMs, it depends on what type of software you want. Are you wanting AOSP, Sense 3.0 or what did you have in mind?
You are wrong about 2.3.4. You simply follow attn1's guide to downgrade: [Tool] Downgrade VivoW with hboot 0.98 - xda-developers