So I had 2 one-way F awards (SIN-NRT / NRT-SIN) for which the flights were cancelled.
I filled in the online form and requested SQ to cancel, and they have done so (don't know the terminology but the two PNR's are still "active" and miles are not redeposited).
I've sent fresh instructions to SQ to open up award space to rebook the exact same flights in Feb 2021 (Currently only Saver Waitlist / Advantage). Hopefully they won't come back to me saying oh your ticket was already cancelled so we can't open up space.