I did a TAS run of Overlord's New Mansion, here:

In the time of making this, I realized the floor clipping in the start of level 8 can easily be done manually, by positioning the camera and then mashing 4+5.

This also works sometimes for the start of level 7, but it is much less consistent for me (If you fail, the enemies give you a ride).

Late edit: In level 15, you can also skip most of the level if you spawn 4 bears manually inside the wall (from the starting position), and then they have a chance to catapult you though the ceiling when you approach them and jump at the right time.

In some of the beginning levels the bears are used to launch you to the door. Is that only do able in the TAS or can that be done in any%?

The way I did the first levels, is do-able only by TAS. One bear can hit you and knock you back a little, but multiple bears can knock you back much further away, as long as they all hit you at the same time. As I recall (I have the scripts somewhere), in some levels I spawned about 3-8 bears in a single "frame" of the game.

You can refer to my current best Any% run to see which tricks can be done manually. Specifically, the trick in level 15 might be a bit shorter than what is used in this TAS run.

How do i get those bears? (i'm new to the game)

@FalcoDash107 Look at the "spawning enemies" guide, for relevant information. For bears in particular you press 5.

It is not allowed in "glitchless" runs though.

why wouldn't you be allowed to spawn bears in glitchless? they dont seem to be a glitch

Well, it's all about semantics really. The act itself of spawning enemies is not really a "glitch", because it is a hidden mechanic the developer put in his game, so you might say that spawning enemies is intended by the developer (it's not).

However, the results of spawning enemies are certainly not intended - you can clip through walls, traverse great distances, or move over spikes. Just look at the TAS or my any% run.

So I split the categories to one where spawning enemies is allowed, and one where it is not. Since I consider not spawning enemies to be "normal gameplay", that is a glitchless category.

we should be able to spawn bears, but not be able to do any glitches with them.

Again, since spawning enemies is not intended for normal game play, just the act of it counts as a "glitch", whatever you do with the spawned creature. If you really want to spawn enemies, you have an entire category just for that (Any%).

on level 15, you can catapult to on top of the building with the door if you spawn 9 bears

In my any% run I did it with 4 bears. Is summoning 9 bears more consistent?