Do you clear immigration on a connecting flight in Singapore?

Probably a silly question, but I want to double check.

I’m flying Perth to Japan in February with a 5 hour layover in Singapore on Singapore Airlines. For a normal connection like this, do you stay airside and not clear Singapore immigration?

I’m asking because I carry personal medication that normally requires approval to enter Singapore, but the rules say it’s not needed if you don’t clear immigration. Just want to be 100% sure.

Also, what happens if the flight is heavily delayed or cancelled and I’m forced to leave the airport? Would immigration then apply?

Thanks in advance, appreciate any reassurance