Anyway to open IDD cs5.5 with 5.5 with CS6 installed?

No, if you are on a Mac, you're out of luck. Macs always default to the newest version of the software. Rokohiko's Soxy is the only way to change this behavior.

You can always use the File > Open Command from any version....

On windows we get to see the correct version icon, so we can tell waht version of ID to launch, but you mac folk aren't as fortunate so you have to either know, guess, or use soxy.

Peter Spier wrote:

 

... so you have to either know, guess, or use soxy.

Or IDentify your InDesign File http://forums.adobe.com/message/4071273

Which only works on one file at a time, by the way.

Pro: you can install and run it on any of your ID versions. Con: you have to run it before opening each file! Con-con: ... but opening an old file in a newer version will add [Converted] to the file name, and you cannot save the document -- in that case you always have to use "Save As".

Oh yeah, your script. Would you believe me if I said that's how you "know" instead of guess?

I didn't think so...