Looks like the cement coating (parge coat or parging) was carried over
the frame in which the cellar door sits. Not that the crack runs
parallel and within an inch or two of the door edge. Note also the
lever is based in that same area.

I suggest removing the parging; cleaning and painting the frame;
sealing the joint between masonry and frame with a bead of sealant.

The window sill looks to be a handsome stone.
If it were mine, I'd seal the joints between the stone and window and
between the stone and abutting walls with a bead of sealant.

The drain I leave to others.

TB