Rollback to 10.8

Good Day,

Mac support after providing me with a lot of misinformation repeatedly now says rolling back to 10.8 is impossible. This has turned my DAW into a brick. It was the Mac store who upgraded it to 10.11 when it was in for minor service. Tried to create a boot USB jump but can't open the package to get to the ESD. Yes the laptop is old but the system was solid. Thoughts? Ideas?

Thanks and have a great day.