Unsure if you need the 是 here.
I'm a native speaker, and it actually sounds much more natural WITHOUT the 是.
Agreed. I considered adding it in, but it sounds less natural.
"今年春节是几号" should be accepted
Can you flip the sentence around, or not and why??
So can it be translated as "几月几号是今年春节"?
No. Chinese syntax follows a Topic - Comment" structure. The topic / subject phrase 今年春节 must come first.
My answer the same and shoukd have been accepted
是 should be omitted.
It makes no sense to add 是 if it is omitted from: 今天几月几号？(What's today's date?)
Im taking the class with a teacher who is a native speaker. When I was taught, she rarely used 是 after year 3