I don't. There doesn't appear to be a serial number for UA Session 2 SONAR Edition. Besides, it only runs in SONAR, so it's effectively tied to that, as far as I can see.
 
It says SONAR EDITION in the logo under the keyboard in the top centre of the UI and in the info screen when you click the logo.
 

 

FWIW and FYI, I had no problem updating Strum Acoustic Sessions (Sonar) from 2011 to Strum GS-2 on the AAS site.  I did notice that in my CW account, the SN for SAS shows the actual AAS serial number.  However Lounge Lizard EP-4 which I purchased  through CW does not match the AAS serial number that shows in my AAS account.
 
BTW, did CW provide us with UA Session at some point?  I don't recall that.

It was added to 2016.03:
 
https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=NewFeatures.001.html
 
It's probably in the Platinum Instruments Collection, although it's not explicitly mentioned in the details in the Command Center.

Ok i have sent a mail to AAS support

Ok i got it with special price!