Don’t worry about the terminology, though it’s important to report error messages, settings and so on accurately.
When you say “nothing works”, have you tried turning the phone off ? If the on/off button doesn’t work, you can remove the battery (you should not do this when the phone is on, as a rule, and impossible of course in most modern phones), wait ten minutes and then put it back in.
If the update was unsuccessful, then when you turn it on again, the phone should use the previous version without your having to do anything. However it may also manage to restart with the updated version. The worst case is if it “thinks” the update was successful when in fact it wasn’t.
On the subject of SD cards, if you have one, make sure you understand about how it can be formatted as “internal” (i.e. used by the phone to supplement internal memory for storing apps, app data and so on) or “portable” (in which case it’s used as though it were an external drive, much like a USB stick). You should choose the latter (portable). Read more here and here.