The dog looks amazing! All the animations are great, I'm glad that I visited this forum

That looks dope and shows new paths in making Spine animations ^^
I am curious about performance. There are some topics that say that manual mesh deform is very very bad, we should avoid this but e.g dog's project has some of them on the timeline.
It would be even more complicated to make same effect but without using manual deform so finally, what's it like with these manual deformations? are prohibited or allowed

While avoiding deform keys for meshes is generally better, how bad it is to use them varies. This page lists the reasons:
Keys - Spine User Guide: Deform keys
The worst case is a mesh that has weights for many bones: each deform key will store a vertex position for every bone that affects each vertex. This can add up to a LOT of data. Other than that, the next best reason to avoid deform keys is that they can be difficult to change. The third best reason is reuse: using bones and weights allows you to use have a different mesh be affected by those bones.

Still, if you need them, you can go ahead and use them sparingly. If you find you need them a lot, you are probably better off setting up a bone to control the deform using weights.

I'm sure you're a magician from Russia

Ukraine magician :grinfake

Super cool stuff, thanks for sharing, as always! The rotation trick is really neat!

Have you seen 4.3? I'm excited to see what you come up with! This thread has some interesting setups.

Oh man, 3.8.99 is almost 6 years old! There are many thousands of hours of improvements: physics, sliders, the new transform constraint, fewer bugs. Oh nooo you don't have a graph in 3.8! The graph view, an improved curves view, the awesome favor tool, keying X/Y separately, sequences, direct PSD import (it's super fast!), 4K icons, duplicating constraints and their bones together, weight locking, mesh weld, folders for slots and constraints... I feel bad that you are missing SO MUCH. Sorry if you're aware and it's out of your control. Maybe management could be convinced the magnitude of the improvements is worth it?

The 4.3 runtimes are more efficient and use less CPU, even though lots more features are provided. The upgrade would give benefits everywhere.

We are available to help your development teams upgrade to v4. They can reach us at: contact@esotericsoftware.com

I noticed in your video some misalignments in the UI, probably caused by using UI scale != 100 or 200. In 4.3 that shouldn't happen and all the text is crisp at any UI scale.

BTW, do you mind if we show off your rotation trick in our videos or tips? We'll credit you for the technique!