بسم الله الرحمن الرحيم
Yes, they should perform the remaining rak?ah of tarawih individually.
(2) They can perform if the imam does not turn to salam at two rak?ah, but if he performs salam at two rak?ah, then you should perform your witr also individually after remaining tarawih.
Allah knows Best!
Darul Uloom Deoband