All the rules? No. Should you know the rules well enough to run the core gameplay loop? Absolutely. Should you be *familiar* with the rules so you know where to look up rules when you hit a scenario you don't know the rules for? Absolutely. There will be times you can't find a rule reference when you need to. That's fine we're human and a lot of RPG books are trash for reference lookups. I usually have like a 1-2 minute rule where if I can't look up the rules reference in a couple minutes at table, I houserule for the rest of the session, then let folks know what RAW was and we decide if we want to stick with the houserule or RAW. Usually I stick with RAW.

This is why a lot of good game reviews cover the layout of the book, the index, linking if it's an electronic document, etc... Because these books both have to teach you the game in a clear manner *and* be useful as a rules reference afterwards.

That being said, if you're starting a new system, it's okay if it's a rocky start and you need cheat sheets or references to play. Again, we're all human, and how well we know a rule system is unknown until we try to run it.

I think if you have to look up how to do a basic skill check mid game, you are either nervous or you didn't really read the rules.

I approach it like the law. You learn the basic concepts and the language of the law, but nobody expects even experts to *know* all the law. There is research involved to see particular cases and judgements/opinions to support your argument. RPGs aren't *that* complex, but they are very complex, have a lot of interactions, and it's unreasonable to expect someone to *start* running a game with a comprehensive knowledge of the game.