Confused

So I start birth control soon and I have sooo many questions. Please help if you know.

1.) how fast do they get to work, like how long will it take to get into my system and start doing will it need to do?

2.) if my period is different than what the packet says do I just take the period tablets when I’m on my period?

3.) After my period tablets will I still have enough medicine in my body to be able to have sex?

4.) if I have sex on my period tablets am I still protected against pregnancy?

My boyfriend and I don’t like condoms, yes I know it isn’t “safe”. I don’t really need judgment I just need guidance. My mom won’t talk to me about these kinds of things.