TIA 15 vs 15.1 backup question

Total Siemens noob here with a likely silly question. I have been asked to go get backups for a few machines that are being moved by a customer. I have TIA 15.1 installed on my laptop, but two of the machines appear to be running with TIA 15.

If I go take these backups with 15.1 and upgrade them - and worst case after the move one of these PLCs loses a program and I have to download my upgraded version - will they still have access if they only have 15 software?

Basically as an AB guy I don't know know if TIA 15 and 15.1 are similarly a minor revision change that won't hurt accessibility if upgraded.

Any other pros/cons to consider? Getting 15 on my laptop is time consuming but not a problem if it means playing it safe.