I hired a pro to finish my floor and he used masterline. I want a third coat, can i use woodline? Also how long does it take oil poly to cure. Mine has been two days and it flakes off if i scratch it with my nail

Most OMU's require a week before normal use and up to 30 days to fully cure. 2 days is not long enough before buffing and re-coating, especially with a different product.

so if i went with masterline can i recoat now which is three days?

You can try. I'd start by trying to hand sand a small area with 180 or grit sandpaper. If it doesn't powder easily or gums up, the existing finish is not dry and cured enough. Many things can cause a solvent finish to delay drying properly. Low temps, lack of air flow, being applied too heavily, inferior chemical properties ( commonly found in consumer VOC products ) and so on. For what it's worth, I once used a Minwax VOC compliant finish to finish a floor. Even with good weather and fans placed everywhere and a 500 ft spread rate, the finish took two weeks to dry enough to buff and re-coat. I swore I'd never use VOC solvent finishes again, and I have not.