1. Pretty sure you can't.
2. Not that I know of.
3. I can't say for sure (as I havn't pulled the nodes nor found I way to see this) but I'm pretty sure that the nodes replaced on systems I've managed were not the same revision as the one it replaced. And I've never experienced any differences on systems with nodes replaced and systems where it hasn't.
I'm just taking a stab here that the revision number changes whenever a single change as been made (ie, change of node disk model or a new RoHS compliance needs to be addressed or other smaller changes to the controller). The speeds and feeds should be exact across all revisions, if not, something would probably break