Q: In the second peer review, I got comments that are completely different from the first review. Is it a normal case?
My manuscript required some revisions at the first peer review and I answered all the comments. At the second peer review, I got the comments that is completely different from what was asked in the first review. I have never experienced something like this in other journals so far. Is it an acceptable for a reviewer to do this?
While it is not common for peer-reviewers to ask a completely different set of questions, there is no hard and fast rule that they cannot. Sometimes your responses or another reading of the manuscript might raise more questions, which the peer reviewer missed in the first check. However, if the comments indicate additional experiments or extensive revisions, you may discuss this with the journal editorial office and ask for more time to revise your manuscript. In addition, if you feel that the suggestions in the second round of peer review are outside the scope of the current study, please bring that up with the journal editor as well. They have the last say on if the manuscript can be accepted and they can take a call on whether all the suggestions in the second round need to be implemented.
It can be frustrating waiting for your manuscript to go through to the acceptance stage; we hope things work out, and we wish you all the very best!