claire:

• must / have to: study harder, keep up the community project, trust each other.
• mustn't: waste time chatting online, think badly without good reason.
• needn't / don't need to: worry if not chosen for the volleyball team.

bob:

• must / have to: take driving test, improve results, get along with classmates.
• mustn't: -
• needn't / don't need to: worry if not chosen for the volleyball team.

both (claire and bob):

• must / have to: keep up the community project, trust each other, not overthink.
• mustn't: -
• needn't / don't need to: -