Hello @Sunil Kalekar
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this!
Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution.
Please click "Accept" the answer as original posters help the community find answers faster by identifying the correct answer.
Issue: Why do I see down time required message when I am just validating the Azure Basic LB & not performing the actual Az Basic LB upgrade?
Resolution: I got to know that there was a bug in the Azure Load Balancer update VALIDATE ONLY code that was prompting "Down time required" prompt. The Azure Load Balancer Team has fixed the code immediately & after the fix we see no prompt of "Down Time required" when performing validate only option.
I hope this has been helpful!
please don’t forget to close the thread by clicking Accept the answer wherever the information provided helps you, as this can be beneficial to other community members.