Father Satan at times will bless someone with a familiar which has the Soul of a Lesser Demon/Demoness.
But as for outright taking the form of an animal at any time for whatever reason, this is enemy gibberish. To do that would require advanced Godlike biokenesis, and even then it would take a long time to transform from their current form into that of an animal. No, Satan puts the Lesser Demon/ness into the animal directly without transforming the Demon at all.
As for possessions no, They may choose to speak through people at times but that's it. The enemy reptilians, greys, and angels along with their cohorts Christians, Muslims, and the Jew are responsible for possessions.
I hope this clears up any questions you have.
Hail Satan The Bringer Of Knowledge.