Since cat is just 7 days away,it is not possible to attempt all the dash cat, so what are the must do dash cat that one should attempt?

DASHCATs 16-20 are very good and are on the easier side. Go for it

Attempt the last 5 DashCAT(16-20) they are closest to CAT level.

attempt 2 easy mocks ( among 16 to 20). and 2 hard mocks (among 2 to 7),,, make sure that you only write mocks if you can handle your emotional quotient when scores falls down in mocks. however, write the mocks woth the sole perspective of building stratergies in order to tackle best or the worst scenario in the actual exam. and if u are really tensed, than i suggest, just write sectionals, dont go for mocks. ease out a bit, take it as an exam...... cheers