Need some help to start playing this game

I'm a new player, I still have a few questions about the equipment system in this game:

1. Sub Parts can be equipped on different characters and still provide their effects. Does the same apply to Main Parts? If I equip a Main Part on a different character, will its full passive ability still be activated?

For example, if I equip Emmelia's Main Part on Kirin, will Kirin be able to activate all of Emmelia's Main Part passive effects?

1. Sub Parts are divided into Sub Part 1 (S1) and Sub Part 2 (S2). If I equip two S1s or two S2s, will both of their passive effects be activated?

For example:

• Can I equip Behemoth's S2 together with Physis's S2 and have both effects work?
• Or can I even equip two copies of Behemoth's S2?

Or is it mandatory to equip one S1 and one S2 in order to activate the full passive abilities of the Sub Parts?