Basically no, this would not work.

That kinda stuff might have worked 20 years ago, when 'points rewards' were a fairly new concept and banks had not fully thought through potential ways to game the system, as you've described...

But they've now had about 20 years of 'clever' people functionally finding all the flaws, and they've since fixed them.

For starters, if you book a flight and then cancel it 24 hrs later, there is no actual guarantee you'd get a full refund.

Beyond that, if the payment was reversed or cancelled, so too would the rewards points be undone.

If you're going to try to get a cash refund... for a credit card txn that was cancelled...

That's basically fraud, you'll go to jail.

Unethical or not, this is stupid, unless you want to be investigated for fraud.

If you want the specifics, go find the exact, precise terms of the agreement you signed when you got the credit card with rewards points.

Chances are high that there is a lot of language that explicitly states that trying to convert points into direct cash is either not allowed, or follows a framework laid out in great detail, where the bank controls exactly what you can and cannot do with the points.