Tejas Mk1A first flight should be towards end of 2021. AFAIK, the Tejas Mk1 prototype LSP8 is being modified to become the first Mk1A prototype.
Tejas Mk2 should have it's first flight in the third or fourth quarter of 2023.
And yes of course, both will definitely be inducted. The IAF is hedging it's entire light fighter and medium weight fighter requirements on them. The IAF ACM Bhadauria calling the Tejas Mk1 "best in class" and saying "take my word for it" tells you how confident he and IAF top brass is about it.And this is also borne out by the reports of how happy the No.45 Squadron pilots and technicians are with the Tejas.
So, now that the IAF knows how good the Tejas Mk1 itself is and that if they are fully invested in the Mk1A and Mk2 programs, they can steer it as per their needs on a single source basis. Compared to that, the MRCA/MRFA is dependent entirely on the MoD and GoI and their Defence Procurement Procedures and how a tender needs to be done.
MRFA contest (same as the earlier MRCA contest) hasn't even resulted in a RFP as of now, only an RFI was sent out. By the time they send out the RFP, evaluate the contestants, receive bids, open the bids, evaluate the bids and then begin L1/L2 negotiations it'll take 3-4 years optimistically. After that, if the bidder gets selected as L1 (as Dassault was during MRCA), it'll take another 1-2 years at the very least to sign a contract with the thousands and thousands of pages it involves due to the complex local assembly requirements and offsets. So that's anywhere between 4-6 years for a contract to be handed to any foreign OEM.
And remember, the IAF only gets it's first foreign MRCA directly from the OEM, 3 years after the contract is signed. Not to mention all the difficulties with setting up a local assembly line for it. So, there won't be any imported MRCA coming into IAF service till 2028-29. That is assuming it even goes through all the hurdles and there is a budget for purchasing these.