What if i no longer want to file my tax return with Turbo Tax, but I already registered? I didn't fully complete the file part yet though is it ok to just stop and not go through with the rest?

Yes, since you have registered you will not be able to clear the return yourself using the Clear and Start over button, but you can just abandon the account and leave it alone.  After tax season is over (October 15th because of extensions) all of the information will be wiped if you don't complete it.  But, please note, you will get a series of reminder emails reminding you to file but you can ignore them.

if registered, am i being charged for it?

if I don't e-file with them do I still owe them money?