If you just want limited liability, you'd go with a simple UG (takes a week and costs 600€, but if you do it right it takes 2-3h and costs 300€).

If you additionally want to avoid being taxed when you sell stock, the entire company, or transfer it to another country, you'd create two UGs, one as the primary company, the other as a holding. That takes 2-3h for both and costs typically around 800€, but can be had for as little as 400-500€.

This is what previous German YCombinator startups have gone with and recommended in the past.

Going one step further, because a UG is so easy to start, banks will refuse to loan you money in the first year, so you can only raise money by selling shares. If you want to avoid that, you can start a GmbH with an UG as holding instead. This will take a month and requires you to sign over at least 12500€ of assets to the GmbH.

Now, what if you want all of that, but you also want a shell corporation to hide the owners and investors? Then you'd start a GmbH & Co KG, where you set up a limited liability corporation, a shell corporation with multiple special classes of stock, and potentially additional holdings. This is what OP went with.

Nope.

But the GmbH & Co KG setup the poster wants is not needed for limited liability.

You get that with a plain GmbH (or UG), which is much, much simpler to set up.

Depends. Given OP built yet another AI tool, yea, I want to hold them liable in case something goes wrong (not that I'd buy these tools in the first place).