I've seen this asked but not really answered. I have a flight into SIN on Cebu Pacific, arriving around midnight.
Have a flight out of SIN on Jetstar leaving at 8am. From what I am reading now, since it's not a roundtrip booking, Jetstar won't provide me with a mobile boarding pass (so, I probably can't use the airside transit between terminal 4 and 2, bummer - although I'll try using their ticket anyway).

In case I have to go landside, is it possible to check in or do a passport check with Jetstar around/after midnight (say, 1am) and go back airside? Or am I stuck landside until their check in opens in the morning?