Originally Posted by
SeanLee
There is a early checkin available at 945pm for the CX714 flight in august, not sure if it will be opened much earlier though. Also it was reported in the SIN telegram groups that for the transfer T4->T1, it is better to do landside as there were reports of being denied transfer at airside. Also you will need a physical boarding pass. After you are done you can head back to T4 using the airside transfer.
According to the Changi Airport website, with link and screenshot below, you need to clear immigration according to your departure terminal.
Cathay's service desk at T4 Row 6 essentially told me the same thing when I asked about entering airside at T1 instead of T4.
I don't know how strictly the Airport enforces this policy.
https://www.changiairport.com/en/faq.html