Refresher is a familiarization flight aka FAM flight(minimum time 45mins)
for the renewal you will have to go to your regional office.For delhi- go to dgca office adjacent to the arrival terminal at PALAM.
Flight schools near Delhi with PA-34 in airworthy condition:
1. Amber Aviation, Pant Nagar, UK (near dehradun)
2. Chimes Aviation, Sagar, MP(near bhopal)
there is another school in bhubaneshwar called GATI, but you will have to check with them if they have obtained the required clearances from the DGCA
PS: Sorry i dont have answers to all your questions.