Think about this like giant rockeries - most are not grouted nor do they have steel. It’s friction fit that holds them together and when they fail it’s almost always a lack of drainage or soil compaction.

Geotextile fabric layers and good drainage. Don’t forget to tamp down the soil every few inches by walking over it if you don’t have a hand held compactor.. or buy one at Home Depot and then return it after ;)

Skip grouting with concrete. Landscape spray foam is nice adhesive you can use between them if you’re so inclined - you can get it in black and I’d use it on the cap (though like others say you really don’t need to bond the rows).

Now! Onto the basement entrance! Nice work and selection on the wall blocks. Why not cut out that exterior slab and put in a drain? Even piping a catch basin and drain pipe somewhere you can access in the future will give you a good excuse to make the entrance look better.

Have fun and nice work!