1. Average velocity of a particle is zero in a time interval. Is it possible that the instantaneous velocity is never zero in the time interval?2. Average velocity of a particle moving on the straight line is zero in a time interval. Is it possible that the instantaneous velocity is never zero in the time interval?

Avg velocity is 0

which means displacement in that time interval was 0.

During the time interval it is possible that that the body was travelling with non zeo velocity at all instants but its avg velocity is 0 as the displacement it covered was 0.

we know    avg velocity= net displacement/ timeinterval

if a paritical is remained static during the whole time interval, then the instantaneous velocity will also be remained zero.

1. yes it is possible....... if in a circular path if the initial point and final point is same then its velocity and average velocity becomes zero but in circular motion the direction continiously changes  and in circular motion the instantaneous velocity becomes non zero