The assessory pouch shown for the 5 and 6 will it fit the 4 sheath?
No (and yes) the mounting holes towards the tip of the blade do not line up, but you'll find many pictures of one mounted anyways. I've got one mounted to a "3", search function is your friend (saying this because the pics are priceless).
Does it have anyway to attach to a regular belt if you wanted to use it as a stand alone small kit?
No (and yes) there are no loops or straps on the back of it, it's clean except for the mounting holes/eyelets. So you can run it with "tek-loks" attached with screws and it will mount to a belt just fine.
Going back and forth will be a real p.i.t.a though, once you mount it either way you'll have to remove screws to change anything. If you'll be using this as a "stand alone" kit I'd recommend you check out the countycomm set-up, which won't really attach to a knife but attaches easily to kit (loops, belts etc.)
Merry Christmas!