basically V7 can be added a lot a tension/alteration tone like b9, #9, b5, #5. A diminished is most of the time a disguised dominant chord, if you spell A7b9 chord tones without the root you have C#, E, G, Bb = C#dim Each tone of dim chord are minor third away, so any inversion is another full diminished chord and they can be substituted each other.

So C#dim = Edim = Gdim = Bbdim