You can play singleplayer. There is literally a singles mode.

It can still happen, but I don’t have that issue myself. I have updates disabled entirely, but I turn it back on once a week to check for updates and install. But something like restarting while I am using it doesn’t happen.

I managed to get a POTG with McCree once while there was a Bastion, but once is the key word. Every other time it was reaper or Bastion.