Great post! Very thought provoking!
I think that you mean: “What is Satan and demons doing in
heaven before he is kicked out of there.”(It does not make any difference to your question when
he is kicked out, 1914 or any other date.)
Here is my opinion:
Satan and his demon
are resisting God’s will and his Holy Spirit in heaven. The war that broke out
in heaven shows that Satan is in opposition to God in heaven.
Seems that Satan (I also mean his demons also) has God given
power and authority that God entrusted to him when he was a Holy angel and he
continued to exercise it, in opposition to God until the war takes place, the
time when God kicks him out. In the Bible, Satan is referred to as the god of
this world and the ruler of this world in connection with the earth. This title
(god) describes Satan’s great power and authority and ruler ship and will over
the earth and humanity, but such great power (god) can only be held from heaven. After the war in heaven when he is cast down to earth (whatever
that means literally since he continues to exist in a spirit realm - but not in
heaven,) heaven is secure and God can
operate from there without opposition and Satanic presence (what a relief for
all the angels-and for God.)
So, what was Satan doing in heaven? Satan had been entrusted with power and authority
when he was a holy angel, (same as when a Sovereign entrusts some entity with
delegated power, nuclear or otherwise, and then the empowered trustee turns on
the Sovereign to achieve his own means or he tries to take over in opposition
to the Sovereign; his time will come when he will be stopped, no doubt about
that, but in the meantime he causes a lot of harm and damage while he is in
power.) he continued to use that power and authority
in opposition to God until the time came when he was dealt with, that time is the war with Michael.