I heard rumors like pilots are required to "memorize" every single letters in every jeppensen chart such as MSA and etc
Absolute rubbish. Whoever you've been talking to has obviously never actually done the training if they're saying things like that.
The training is long and it is tedious. There is no reason for it to be as long as it is and they could probably cut it in half very easily and 66% wouldn't be too much trouble.....but they won't. It's just a slow race to the finish.
The actual training is not difficult but it's not training. The Japanese learn by rote and they assume that everyone else does. SO guess what you've got to do? In ground school you do have to learn ridiculous numbers like airport design splays etc but you're given a very good idea what you actually do have to learn. In the simulator you're expected to turn up having studied all the stuff that is relevant to the session and you will still be asked irrelevant questions that you won't know the answer to but the instructor does, so he's very clever and knowledgeable. You say 'thank you for your wise words and instruction' and get on with the sims. During line training you will get five different versions of the same way of doing things and according to who you're flying with, that's the way it's done. See above for your response.
You'll get some instructors who expect FOs (they don't normally question captains because they are all-wise) to know the names of VORs, instead of XMC etc but once you're checked out they really don't care. If they're talking about things like that then you're doing okay.
So, in summary, it's long and there's plenty of trivia but memorising MSAs etc is just nonsense spouted by someone who's probably never set foot in Japan.