Hmm, I can’t think of any reason why 2.1.6(1) would affect remote access — if you can access it locally on your network, then the rest is just port forwarding on your router.
To roll back to an earlier version, first go to the commit history:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/commits/master
and identify the version that you’d like to roll back to. Then do a ‘git checkout xxxxx’ where xxxxx is the commit ID you can find out in the commit history. If you google ‘git check out an older commit’ you will find other ways to roll back with various options.