sell gear no one can equip?

[flavie]

Can we sell equipment (a weapon for ex) none of the party uses?
Does items left from a playthrough can be used for a next playthrough?

Well I'm not sure to replay.. there's the curiosity about the 2 protagonist chosen at the start and their relationship that can be a surprise.
I've chosen to be Laura who loves Danny (if I'm correct ) will Danny save Laura or will we discover something about one of these two?
I've read a french steam review saying:

Spoiler: show

"I've named my curse Voldemort. I learn that I must rescue my love Voldemort

[Indinera]

Can we sell equipment (a weapon for ex) none of the party uses?

Yup

Does items left from a playthrough can be used for a next playthrough?

No, items aren't carried over.

I've chosen to be Laura who loves Danny (if I'm correct ) will Danny save Laura or will we discover something about one of these two?

Not sure what you mean xD
But you play as Danny, although once you've rescued Laura, you can play as Laura too.