Look like a weathered limestone to me.
Very commonly seen many in many places on the East Coast. Lots of old old stone walls & farm foundation in the area of Frederick, MD & north.

A large building stone producer quarries something very similar near Evans Mill, in upstate New York. Much in Missouri and Ohio as well.

Repairing is not practical. Check for replacement at a local landscape supply or stone yard. You should be able to buy that kind of grade material for 6 to 8 cents per pound on pallets. Ask for "Wall Stone", *not* "Veneer Stone"

Oooh, a little geology puzzle!
What you have there is a stone that contains two different types of rock within it. You can see where the crumbling parts are all within a distinct layer that is greyish. Meanwhile the whiteish parts remain solid.

My guess is that the greyish weathered sections contain clay or little shaley parts. That is weathering quicker than the rest of the rock. There's not much you can do to slow that down, although arranging the rock so that the layers are not oriented vertically might help. (Orient the layers horizontally and maybe less water will get in between the layers.) You could also flip the rocks so that the stronger whitish layer is on top and that would hide the crumbly part.

There are many rocks that are resistant to weathering. Igneous rocks such as granite or basalt are bombproof. Well-cemented sandstones are lovely, as are their metamorphic cousins, quartzite. Metamorphic rocks such as gneiss are also robust. I'd avoid rocks with lots of layering such as slate (but some slates are OK), shale, thinly bedded limestone or poorly cemented sandstones. By poorly cemented I mean that you can rub or chip out some of the sand grains.

I hope that helps!

Rocks that fall apart make good rock gardens in the naturalistic style. As the rocks age, small talus slopes are formed, making the alpine look more realistic. The weathering shows up real fast depending how soft the rock is.
As a landscaper I built many rock gardens using rock from the Duwamish Formation. It would slowly fall apart like an Alka-selzer tablet. The quarry with that rock could never get certified by the state for walls for highways.
I never used any rock, like a ring, around the flower beds.
It doesn't work for two reasons. It's high maintenance in that it doesn't keep the grass back and trimming the grass with stones in the way even makes it harder. Second, it doesn't look natural. More contrived than anything else, and
usually the work of an amateur.
Mike...retired