Its a product call Criblock...you can find it on the internet.

how do you maintain the garden.

Weeds have not been a big problem...a ladder is used to cut back the dormant grasses...although the wall is climbable. Due to the batter of the wall face, it can be irrigated from spray heads along the top.

Are there caissons or deep foudational support below ground?

I believe there are caissons that go back horizontally into the slope. check out the mfr's web site.