It is the "changes" that have been moved to the test server. Because they are in the plural, you need to use "have been" which is the plural. As for your second question, I'm not sure I understand.
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Netpicker9In this case I am not refereing to a person, I am talking about a code block which is moved from one server to another.
Question 1:
Which is correct?
Website changes have been moved to testserver.
or
Website changes has been moved to testserver.
Question 2:
Is there any grammer table/matrix which shows how to for
I wish to inform to everybody that due to a technical problem the schedule of election has been moved to March 12-13, 2022.