Can I use TWRP to load older ROMs?

Are ROMs connected to a specific recovery? Or can I install the latest TWRP and use it to load an older ROM, e.g., CM11 Snapshot?

Apps still thinks I have older version 4.3 after CM12 install?

I just installed CM12 with correct gapps and phone is working fine. I did it so my kids could download Pokimon Go as pokimon wants a new version then 4.3. After hours of cruising the info on this formum I was able to root, install twrp and install CM12 and the gapps. It works great. However, Pokimon still says I have an older version. I checked in my settings and it says I now have 5.0.2. Is there something else I can change to let pokimon on this phone!
The rom I installed is: cm-12-20150116-UNOFFICIAL-t0lte
the gapps is: pa_gapps-modular-pico-5.0.1-20150221-signed
Thanks to everyone on this forum and the wealth of knowledge.
DC