If you have read the news then it's clearly says Govt is amending Articles 15 and 16. It' not just a simple law. Also curently there are many states where reservation is already greater than 50% like in TN where it is 69%
Yes. This can be done on state by state basis, but when it comes under pan-india then i wonder if it can survive SC, if it does, it might be a huge miracle.