Is it worthwhile to reverse engineer a lens?
While some vendors can do this, it really isn’t worth the effort. While you could measure each lens element and get its radius, you then need to find out the refractive index of each piece of glass. Then you need to get the spacing between the elements in the lens but sometimes in taking apart the lens you wind up destroying it. Finally even if you succeed you don’t know the tolerances for the lens surfaces, the coatings, the centration tolerance or the spacing tolerance.
The time and money to do this doesn’t really pay off compared with making a new design.