I am not sure whether it is useful for you, this question appears on my last Saturday 032 exams, although I do not know whether it is a counted question, since there are 73 questions, and only 64 of them are accounted.

As the backup recommended by Oracle for NOARCHIVELOG:

You should backup your datafile and controlfile, not online redo file.

when you restore from a backup, you can only restore datafile and controfile.

your online log can not be used with your restored backup. You have to reset your online log, which can be achived by open database resetlogs.

in order for you to execute open database resetlogs, you need to perform incomplete recovery.

To pass your exam, remember this is recommended.
In your real career, just backup your online redo log, and restore it. In this way, you can open database normal.