I have mostly been flying BA/AA/CX and am pretty new to SQ (though I am *G)

I am flying BLR-SIN-SFO/SFO-SIN-BLR
Dates are 9/8 & 9/22. The flight is in Y

I was able to select seats for all flights except SQ 2 on 9/8. Most of the seats on the flight are showing blocked on EF.

Questions:
1. Does SQ allow *G to select blocked seats (not preferred, just any regular aisle seat)
2. Does SQ open miles upgrad/award seats a few days before flight?
3. I am not sure but I think SQ doesn't do airport/OLCI upgrades for cheap, is that correct?