Onstage vs. on stage

Hi,

My colleague and I were just wrestling with this one and were not able to come up with a concrete set of rules, nor were we able to find any good examples on the Web.

Merriam-Webster states that onstage is an adverb or adjective. Some of our usages of it seemed to be neither, but I was not able to decisively say why.

For the following examples, would you use "onstage" or "on stage"? And can someone explain the whys to me?


Please help.

Thanks!



I didn't find the right solution from the Internet.



References:

forum.wordreference.com/threads/onstage-vs-on-stage.619529/

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