ds2020
How long does it take for status-under review to change to an Interview call or a Reject? My R3 application is still in the Under Review Stage.

I don't have a direct answer to your question, but I applied R3 and got an interview invite last Monday (1/14), and then my status immediately changed to "Schedule Interview."
In my interview I was told that they were interviewing more people than normal this round, and that it would take about 3 weeks to receive my decision, so sometime in the 2nd week of February. I would imagine that most people will have a decision by around that time as well. So, don't give up hope yet, there is still a bit longer to wait!