The whole point of a hot backup is the database is running at all time, so as soon as you see anything with "startup" in it, or "alter database open", you know you are not dealing with a hot backup.
Backup and recovery is to important an area to try and skim through. You have to hit the books and understand it. One failed backup and you've potentially lost your job!
Start here: http://www.oracle-base.com/articles/9i/ ... ger-9i.php
Read all the enhancements articles it lists for newer DB versions. When you understand the points in these articles, you will be ready to consider going near a backup. You will still not be an expert and you will still have a long way to go, but you will be at the start of beginner level. Before then, you are dangerous and shouldn't attempt to do anything with backups!