Nafl Qurbaani

Few people slaughtering one sheep for Rasululullah (Sallallahu Alayhi Wasallam)

Q: A group of students get together to get a sheep slaughtered for Qurbaani for the Prophet (Sallallahu Alayhi Wasallam). Will the Qurbaani be invalid since a group of people cannot slaughter a single sheep, or will it be valid since if they intended the slaughter to be on behalf of a single person (i.e. the Prophet (Sallallahu Alayhi Wasallam)?

Nafil Qurbaani

Q: When making nafil quarbani for one's deceased parents and our Nabi (Sallallahu Alayhi Wasallam), would one share in an animal suffice for all or three separate shares need to be purchased?