Singsaver exclusive offer on free Airpods pro when applying for Citi Credit Card. What is the catch here?

The offer is only valid for new citibank customers, and the condition:

"Airpods Pro are subjected to the availability of third-party distribution and supply channels, over which we have no control. In such circumstances, eligible cardholders will instead receive a reward of the equivalent value, as determined by SingSaver acting in its absolute discretion"

Yes, you can apply for the rewards then cancel the card subsequently. Have to bear in mind, you may not actually get the Airpod Pro if that's what you are going for.