I have CC LR perpetual license.
I wish to add Lightroom Mobile to my CC.
Can I add it to the Perpetual License?
If not can I purchase monthly/annual etc license for LR Mobile and retain the perpetual license for LR?
Sorry but Lr Mobile is only available to the CC subscription option. Your version is 6 not CC to avoid any confusion between the two.
You have to subscribe to get access to Lr Mobile unfortunately, it is not available the way you ask, sorry.