it is that simple. You go to a catholic church you need to learn the basics before you take communion so you know the rules per that churchs doctrine you choose to live by them or not of course if you choose not you can go and confess simple
If you are a JW you have to do bible studies and learn a certain amount before you are baptised you then choose to live by the rules or not simple
You are a Muslim and go to the Mosque I am pretty sure they teach you the rules early on you then choose to live by them or not simple
The differences in religions are complicated whether or not you live by the laws of said religion is you got it simple
edit these points directly to the faith as being followed and whether folling a doctrine is choice or part of the doctrine. So identifying if its doctrine or personal relates to topic of females being allowed to mix with males (just to show I am not deliberately posting off topic)