What foundation is needed for a garden wall?

The picture in #1 shows simple shuttering blocks. You can get those at any hardware store. The picture in #12 shows colored concrete wall blocks. Every manufacturer of concrete paving does that. It's best if you go to the nearest building materials dealer; they usually all have a small exhibition with garden construction materials.

I actually mean which stones we should alternatively look at that have a similar appearance?

Completely concrete the area and either scratch the stones into the plaster or paint them on would also be an alternative. I mean that seriously. There are hundreds of videos on YT and Insta showing how it's done. It looks sometimes deceptively real. But I don't know how widespread this is here and whether you need special material for it. It seems more like an American or Far Eastern thing.

I actually mean which stones we should alternatively look at that have a similar appearance?

As I said, just go to the nearest building materials dealer with a garden construction exhibition. You should find enough there. With the smooth appearance, only concrete stone really makes sense; natural stone is far too precious to be cut to a perfect size.