I have one 15 amp line that runs lights and garage door opener. I added a couple outlets for work bench off this line. The 20 amp line is on the back of the garage for fridge and runs up on the front of garage for 2 outlets. Is multiple outlets on 2 different breakers OK?

Absolutely, actually it is recommended. Remember that all 120 volt receptacles in a garage need to be GFI protected.