I am looking onto the seatmap for TK165 from SGN to IST on 31 October (not my flight). in Expertflyer. Looks like the seats have been pre-assigned already and the middle section is left open for balancing needs.
The aircraft is 35E. The new version with 3 rows of 'PE' seats (made for SU).

The 'PE' seats are already pre-assigned (all 3 rows from 8 to 10) and looking into the seatmap i have a feeling that these were not sold but just assigned.

If anyone can advise on the following please:

1) If seats are indeed pre-assigned who get those for free?
2) Is there any discount for extra legroom seats during check in compared to pre check in time (might be logical as normal seats would go for free)? Should we add this point to the wiki?
3) Any benefits for Star Silver for seats selection at the airport or during online check in?