They certainly are.Quiet a number of times, the short answers are framed out of those only.
additional exercises of ncert have some good concept building questions.So they are good for competetive view but they are never asked in final exams.So if you have time you may go through it
No..they are not much important in point of view of exam...however they may be included for your class tests and mid session..but not for final exam....for us it is told so..but if u want,u can just go through it..that's it my frnd.. 

plzzz mark as the brainliest answer