I'm also assuming that all version of Core will have to be the same release.
It's not a hard requirement.
But there are a couple of latest incompatible releases to watch-out for (
I wont mention older compatibility issues):
- If you've used v28.0+ to sync a new blocksdir, those blocks can't be used by your other v27.2 Bitcoin Core instance or older.
This is due to the new block files being XOR'd. - Your old legacy wallet.dat files can't be loaded to v30.x anymore with them being migrated into a descriptor wallet.
Other than those, it's relatively safe to use different versions of Bitcoin Core.
