1. Moving circle.
2. Platformer.
3. 3d shooter game with 2d engine
4. Real time action rpg.
5. 3d shooter game with 3d engine
6. 3rd person exploration game
7. more 3d action with less shooting
8. again 3d with more shooting
9. and again with less shooting
10. and more rpg
It is pretty much using a 3d engine at some point. With Skyrim there is even a blur between first person and third person, as you can zoom into first person and out into third person. But the later games in your list are more about the story they tell. You could tell Skyrim in rpg maker. Or even as a visual novel. It would be very hard to mimic their core in such a short game as you plan it.
What you try to do reminds me of this game Evoland.
And what is "missing" are a lot of genres. Like puzzle or racing games.
With something simple as pong you could use your own things, but in complex game engines, many lifetimes of programming went into them. While you might re-create some aspects or a barebone version of it, you simply have not the time for that to finish your project. Of course you might use more advanced graphic libraries, but the line between libraries and a game engine is fuzzy.
Programming itself is easy and very hard. You just need to know what you want to do, and solve it within the capabilites of the given environment. So "cloning" something as an excercise would give you some guidelines what to do.
You could arrange those projects as minigames within a game. Or do you plan to switch engines for each project?
There are just so many game genres and mechanics. If you had some goal in mind, you might work towards it by picking out mechanics you would want to see in your future game and play around with them. Things like item and ressource balancing and having a combat AI are hard. Creating a puzzle is a different kind of hard. And creating an interesting level layout yet another type of challenge. All part of game development, but less of a programming problem. More of a game design task. And then there is of course story. The Elder Scrolls series did benefit from engine upgrades, but ultimatly it is story and the huge world and all the details that made their appeal.
More games you could recreate your own take on, as an excercise:
Slay the Spire. Cookie Clicker. Maniac Mansion. Tomb Raider. Worms. Flappy Bird. Plants vs Zombies.
Oh, and Diablo had no branching of any sorts. It is an action rpg. You chose how to beat the boss. Not if you beat the boss. Same for practically all the games on your list. There are no choices but how you level up your character or what tactics to use. Branching is more like visual novel territory. Dialoge trees usually just give illusion of choice, or you select wich upgrade to get. Or flavor for rpg.