I looked around at the web site to answer some of your questions (
www.millipiyango.gov.tr - unfortunately no english pages ) :
- The main office is in Ankara and from 1 million on , they pay.
- There are offices in Mugla , Antalya etc to pay prizes smaller than a million
- The sales people ( like those on the street ) have to pay the prizes up to three digits ( from right ). It's up to their decision to pay for the last 4-5 digits.
- You could write your name and sign the back side of the ticket , so to prove you are the owner. If you win a great prize , they would want you to do this anyway at payment.