A guide or something will be most helpful because I doubt I can learn everything only by playing the game, or am I wrong about that?

I know I have a lot of question, but please help me here because 'till today I haven't read anything about Diablo 3 before so any tips and informations are kindly appreciated. I mean, it's Diablo 3 like World of Warcraft? You level up a character to 70 and then start grinding do get the best loot possible? Do you have a main character like you do in WoW or every season you start from scratch with a new character and start grinding on that one? Can I play any class I want or some classes are totally not worth it in terms of endgame content (during seasons or even at all)? I just spend a little time on internet looking out for information and I saw something about new seasons that starts every 3 or 4 months or something, that being like some endgame content. Will I be overwhelmed by the content at first? There is guide out there that I can check to find out what should I know?

Also, I want to mention that I'm more like a casual player and I can't spend so much time in gaming like before (I play mostly in weekends and maybe 1-2 hrs on some work days). My question for you, guys, is how friendly is Diablo 3 for a completely new player? I mean I never played D3 before and I know almost nothing about it. Diablo Prime Evil Collection is right now on sale on Battle Shop and I'm interested only in Diablo 3.

Can 4 people play diablo 3 on one ps4