Join Date: Feb 2013
Location: SFO, MNL, SIN, HAM
Programs: UA GS, SQ PPS, IHG Plat Amb, Marriot Gold, Hilton Gold, Club Carlson Gold, Accor Plat
Posts: 489
Are all flights on one ticket? If so, you should be able to access your full flight on LH website (with the LH booking confirmation, not the SQ confirmation) .
That has worked for me in the past, including seat assignment.
I never tried upgrades...