How to write a scene which was unfolding even before we witness it(like in media res) eg: is it ok to write “Mike is reading the last page of the magazine when the receptionist entered” or is it “Mike reads the last page of the magazine. The receptionist enters”. Not sure if my example really projected the need but I seriously could not decide which one seemed appropriate.

And is there any exception to the simple present. You’ve mentioned people use other tenses on rare occasions. It will be very helpful if you could enlighten me by citing an example of such occurrence. Thank you

The active voice is more impactful. This underscores my point about the literary voice, which doesn’t translate intuitively to the screenplay. Scripts, in general, are about how the protagonist is propelled through the world. In that case, I am not sure what specific benefit you would have in writing “a fire is seen.” Seen by whom, in what context? Why not just state the context explicitly. The protagonist sees the fire. Better yet, detail the protagonist’s relationship to the fire – did the protagonist start the fire and then runs away? Does she run directly into the fire?

If the active voice is still unclear, read more screenplays.