some questions
(1) Personas - do Personas you get in dungeons automatically get registered? I know if you level your Personas you need to re-register them to have the new stats/skills/levels recorded but what about brand new Persona (cards) that you get from Dungeons?
(2) Passive Skills - Do passive skills of inactive Personas that Yu bring along come into effect during battle? Or only the passive skills of the current ACTIVE Persona?
(3) Critical Cast - Is there a passive skill that allows for auto-cast critical?
(4) Stacking Skills - Which skills stack and which passive skills are most useful/recommended?
1) If they're new, yes. If not, then no. It's up to you if you want to register the persona you got in the dungeon via random shuffle. I don't see why you would want to do this though.
2-3) Going to leave these to someone else to answer them.
4)Any of the buff+mind charge+power charge equivalent to mind charge will stack. I think that's it. Someone can correct me if I'm wrong.
General tips for P4:
Even though I recommend not to follow any of the tips and do a blind run first to get the optimal experience, I'll share some.
1) Beat the dungeon as soon as possible- more time to max social links with your teammates.
2)If you want to max social links in your first run through: Use the shrine at night and always save before using it. You always want the max luck charm.
3)SMT rule: always fuse to get stronger persona/demons.
4) Physical Attacks are seriously overpowered in this version of Persona 4. Keep multiple hit persona with crits skills like sharp student.
5)If you really want an easier time with P4, if you see a gold hand, go up a floor and then go back. That gold hand will be respawn at that same floor 75% of the time. To coincide with 4, just spam physical attacks. Thus why Chie is probably the best partner for your team since she is really useful against them.
6) The last party member to join is also overpowered in this version. Let that person join your team equipped with a ring that reduces your SP and you will have an easier time in the optional dungeon later in the game(if you manage to unlock it).
They made P4: the golden easier than P4, which was easy before. However, the Persona games are a great breakthrough to the SMT series. Enjoy the game since it will probably have a lasting impact on you.