"What is a scenery... to you?"

Definitely. In the context of your challenge series I wouldn't assign a different meaning to it.
In another context however it can be a stage of a theatre, a setup on my dining table in a relatively small space…
In the theatrical sense it could be a single bench too.

Probably, because landscape is the native format for scenery but I wouldn't be so strict with the format. (e.g. waterfall)

I wouldn't totally exclude bokeh. You can have foreground flowers in landscape scenery that should be still OK.