Can't Remove/Detatch Bones/Modifier/Vertex Group I'm trying to rig and god is it a nightmare.

I need to undo some bone attachments that I did because they pull the wrong part of the mesh except blender is not build with backtracking in mind. (ex : Ctrl-Z is not an undo shortcut it's a crash shortcut).

After giving up on undoing bone attach, I am instead deleting bones.
this is however proving to be another can of worms because I have to delete :


Bone per mesh
modifier per mesh
vertex group per mesh


the repetition I can deal with however I cannot for the life of me delete vertex groups.

I can't figure out how to use this script I downloaded : 
https://gumroad.com/l/Gxkbp

I have it installed an enabled but I still can't find where the context menu for deleted vertex groups is.

I just need to delete those goddamn vertex groups so I can get on with my life and finish rigging this tank with 7 meager bones that I've been trying to rig for thee days straight.
You can either do it with a brush in Weight Paint mode, or in the Properties panel > Object Data > Vertex Groups, select the vertex group in the list, select the vertex you want to remove in the 3D view, click on Remove button under the list.

Note that on the right of the vertex groups list, under the + and -, you have a down arrow that gives you additional functions, like Remove From All Groups.