I have Photoshop & Premiere elements 9 and have purchased the upgrade for both to v14. I have AVID ProTools 11. I have Mountain Lion 10.8.5.
I run a home studio for music and film production.
According to the online research I've already done, these applications can only co-exist and operate on Yosemite OSX 10.10.x.
Yosemite is not available through Apple's Online store.
While I could upgrade to El Capitan, Avid advise they have no intention of modifying PT11 to make it compatible; they would prefer you change to their annual subscription product equivalent (ProTools v12).
I'm very happy with ProTools the way it is.
If I install the two Adobe v14 products on OSX 10.8.5, will they work or am I going to initiate unforseen problems?
It might work -- but I can't guarantee Premiere Elements 14 will work on such an old operating system.
I'd recommend you download the free trial of Premiere Elements 14 from Adobe.com and give it a test drive. See how stable it is on Mountain Lion.