Depends really, course the whole main casts will be in the game. However, no big spoilers will be in. Basically, it takes place when the whole cast is complete. At least, I think so. Though, Kamoshita is in there by the looks of the trailer..

PQ1 was technically canon, but irrelevant so there's no need to play it first. As for the others, the PQ games typically give you an overview of the cast as well as maybe a TLDR of their backstories, but remain free from any major game spoilers as they do something totally unrelated so its fine to go in without knowing the casts of 3 or 4

Can't speak for PQ2, but judging by the original PQ and the little I've seen of PQ2, there will be at least a few spoilers, but the game will try to shy away from anything major if it can. As Micah said, it's at the point where each team is complete, so it's inevitable that you'll come across certain spoilers for characters, including team makeup and details of certain characters (Naoto is the biggest offender if you haven't been spoiled on them yet). tl;dr don't expect any game-ruining spoilers, but do be aware that the game will reference spoilery details from time to time.

Thank you everyone for your feedback that helps a lot I plan on finishing P4 and starting P3 until I get the full roster before I start Q2 so that way the roster is still a surprise for me. Once again thank you to everyone that messaged it helped alot!

No problem dude, have fun!

The most spoilery thing in PQ2 is Akechi’s interactions with the cast (especially certain characters in P3) but other then that it’s very spoiler free (too me at least)