If you do "google" search for "Botox Penis lengthening" you will come up with sites that somewhat answer your question.
I am not sure abut the cutting of the muscles as they are along the penis.
Here is some information
Doctors made four injections around the base of the penis, with the goal of paralyzing the muscles responsible for the shrinkage reflex, known as the
tunica dartos. And it worked.
Less traumatic and you can try it and if not liking it it will reverse in a couple of months. I believe that cutting comes very close to nerves to penis also. Botox does not affect these nerves.
In
a 2009 study, researchers used Botox to try and help guys who had a "hyperactive retraction reflex." In other words, these were men who experienced a lot more "shrinkage" (in the words of George Costanza) than others. Doctors made four injections around the base of the penis, with the goal of paralyzing the muscles responsible for the shrinkage reflex, known as the
tunica dartos. And it worked.
Methods. Ten male patients complaining of a short penis exclusively in the flaccid state, despite normal and satisfactory erect and outstretched lengths, were selected for the study. One hundred units of BOTOX were injected into the dartos muscle.