Our existing cluster is on 8.6.0.4_74969. I don't know what version the new ones are on. The label on the box has a date of 11-8-14 if that helps.
The whole reason we got the matching 215's is so we can plug them in, let them autojoin and be good to go.
I've never had to SSH in to the AP's, or anything else for that matter, so I'm not familiar with the process. If there is documentation on how to get the info you are looking for I'd be happy to get it.