Can/How Can I replace El Capitan with Yosemite on MBP

I bought a used MBP, a Mid-2015 Retina, i7 Quad. It came with El Capitan installed.

I would like to run Yosemite to allow for compatibility with a particular app which is

unstable in 10.11 but said to be ok in 10.10.

I mistakenly upgraded from El Capitan to High Sierra. I then did a Time Machine backup,

and attempted OSRecovery hoping i could revert to Yosemite - which i THOUGHT was the

OS this particular model/build originally delivered with. The only option given was to revert

to El Capitan.

IF I were able to create a bootable Yosemite USB installer drive, could I run it on this machine?

Or, am I limited to El Capitan or newer?

If i CAN use Yosemite on this machine without any issues, could I still backup content from the

Time Machine backup (done in High Sierra) to the HD after installing Yosemite?

Hope you can help! Thank you very much!

MIke