You’ll want sudo snap set core refresh.timer= as documented here. As for ‘to what level’, an epochs feature is being made which will ensure that updates that are incompatible with previous data formats etc don’t happen, but otherwise you’re automatically updated to the latest version of whatever channel you’re using. You might want to make a new topic if you want to develop your idea further, whatever it is, it would be a snapd feature rather than a snap so it’s not really appropriate for this thread.
You can use snap install python0 for Python 0.9.1? 