Taking Back up on Non readable Secondary Replica Availability group
Backups are only allowed in readable secondaries, so not really. 

Also you need to take in mind that running checkdb might be considered a production workload if you don't run it in production too. 

You should be running checkdb on all your databases regardless primary or secondary and also your backups, that way you wouldn't have to license the instance where you restore your backups and run checkdb on them (you are validating backups, not production databases), otherwise MS can make you pay for that, but I'm not a licensing expert, so better ask to confirm this point.