During Pitru paksha period, should the tharpanam be done before tiruvaradhanam? During this period can one render kainkaryam at temples or mutts by participating in recitations?

As for as rituals such as shraddham, etc. are concerned, tiruvaradhanam precedes tharpanam. Only on masa pirappu days, if the month occurs early, tharpanam precedes tiruvaradhanam.