Does this look like asbestos insulation

AFAIR, asbestos mastic is much more likely with tile (which may itself contain asbestos) - I would not expect it under carpet, other than as a remnant of a prior tile job (no sign of that here.) And, as you have noted, it doesn't look like it.

While you could engage full paranoia (as the folks that make money from it like) and have it tested, you can probably remove it without too much concern, and if it's "gummy" you might want to take a "solvent and wipe up" approach anyway, which would minimize anything getting in the air.

No, it is plaster with animal hairs in it, probably pig or cow hair.

To determine if there are asbestos fibers inside the plaster, break it apart and examine with magnifying glass. Asbestos is a fine white fiber. It looks like this:

The fibers on the right are asbestos, those on the left are animal hairs. Asbestos fibers will be colorless, very fine and clumped together, like in the photograph. Animal hairs tend to be by themselves and have color. Notice that an animal fiber will be rounded, but asbestos tends to be stiff like a corn stalk with crinkles or breaks in it.