Q: How do I wipe El Capitan off my I mac and load snow leopard from the disk?

Wow, I have been trying since last night to post....

these boards went down as I tried... ok so we're back...

I wrote a good reply but apple.com runs a script that crashes my browser...

I will try to write it again... fast

Thank you DC- I managed to get it back to 10.7 using Internet Recovery (for anyone trying, use Command R).  Evidently Internet Recovery has Apple check what your computer shipped with and lets you go back that far.   I happen to have a 10.7 back up of my father's computer (upgraded to ML against his wishes, so I put it back to SL, but that was 2012, and his computer is likely as old as mine, 6 months older than this new one).

So now it's on 10.7 and I checked the firmware as you suggested, the "new" one is MBA41.0077.B12 and my old one is MBA31.0061.B01 from About EFI and SMC firmware updates for Intel-based Mac computers - Apple Support

except that my old one is .B01 as I tried to write here, but that page has it .B07

So this is firmware on the logic board, not the hard drive?

I have the original install USB "chip" for my Air, and if there were discs I'll have them as well.  I'd be happy to take a trip to hackland, if i could figure out what to do.  I am hanging on to what you said about having a MBP that shipped with 10.7 that is happily running 10.6...