I want to create a little proof of concept/prototype/demo game before I move on to making a complete project. A platformer with just one level.

It just so happens that I am also an artist, I intend to do all the coding and artwork for this game I am going to develop, I don't have any experience to talk about with animation (I'm planning to learn it, it's one of the reasons I decided to make a game in fact, 2 birds in one stone sort of thing) but I do have pretty rich experience in coding and scripting.

I looked around and found that the game engine that seems to align the best with my goals is Godot, so that is what I am going with.

However that's as far as I got in the development before confusion set in. Where do I even start?

Should I make a 3D platformer (like Oddworld New'n'Tasty or My Friend Pedro)

Should I make a 2D platformer but with 3D character models/Pseudo 2D (Like Ori and the Blind Forest)

Should I make a more traditional 2D platformer with frame by frame animated characters like hollow knight?

Or should I make a 2D platformer with sprite/vector animations (This is the most common type of animation for platformers I think, can't think of a specific game though, except every platformer ever created in adobe flash of course)

There are pros and cons to every approach, vector animation is in my opinion usually the ugliest. 2D backgrounds with 3D animated assets looks prettiest but I don't know how difficult it is to achieve (I have minimal 3D modeling experience, but it feels highly intuitive to me, the only things I'm unsure of in this area are textures and the rigging/animation part), my original plan was to do frame-by-frame animation but it seems like it might be the hardest approach so I'm having second thoughts about that. Me with my lack of animation experience is quite simply a little confused and intimidated by the complexity of making this choice. Especially since I don't actually know the process for any type of animation (I only have a rough idea of it for all of them). Are there any important options I am missing?

I'm still leaning towards frame by frame animation but if making my 2D platformer in 3D isn't much harder to implement it's an option I'd seriously consider. Especially the pseudo 2D option, but I have no idea how that's done or if it's harder or easier than plain 2d or plain 3d.

My second problem is the level/map creation, or specifically creating the backgrounds, I just don't know how that's done, I don't know if there are different ways to do it, I don't particularly like tilemaps, I prefer having the sort of freehand looking backgrounds you find in for example Ori and the Blind Forest, how should I arrange that?

Then after figuring out the answer to these 2 questions, my 3rd one would be where do I start? Coding or asset creation? how many assets to create before I get to coding/implementing? When animating, depending on my choice of animation style, how do I implement my completed animations (let's say made in krita for frame by frame or blender for 3D) in godot? What's the first thing I should do before I have assets created? What's the first thing I should do after I have assets created?