You’ll get nothing for TR flight.

I credited to SQ for my flights this summer that were SQ/TR, but I didn’t need the miles/PQP - these were relatively regional (SIN-BLR, BLR-CNX) - and even the SQ flights were only going to get me 10%. So just not worth it. (Plus, using SQ number gets free wifi on the SQ flights, though I’m told you can supposedly add your SQ number at SQ desk to get free wifi onboard, yet still credit to partner, but I don’t think there’s many data points on this yet).

There may be a way to credit SQ segment to UA, then have TR go to SQ, but not sure and never tried. I suspect the safest way would be to credit the entire itinerary to UA, then call SQ to retro credit the TR segment(s) to SQ. Maybe an SQ rep can change the FF after arriving in SIN for the TR flight, but without knowing 100%, would be too afraid it would also change the just arrived on SQ segment as well. YMMV, I guess.