Umm i have not been in touch with WPcentral and now windows10 mobil version is available as TP, I'd like to know how to install w10 TP on lumia620.Probably.
But remember, a big thing I've noticed is that YMMV. You may need to erase the phone in order to get 10 to a working state, or not.
As long as you're ok with erasing the phone (backed up whatever you need saving, don't mind losing some game data...) its worth a shot.
Ok, hope the new build 10512 Will fix all those and much more, I'm planning to update, but i hate bugs!