Yes the only way for you to play backups is buy a downgrade device. Almost all of them you need to solder. What you can do is to check the firmware on your ps3. And if it is 3.70 there is no hack right now for that and the only thing you can do is downgrade. The other thing you can do is buy another ps3 that is on 3.55 or lower. Check eBay or old stock at retailers.
This is why when you are on cfw and it asks you to update YOU DON'T. There is a mod offering a downgrade service for the ps3 in the for sale section. Thanks and hope it helps.