If differences that are not to be changed need to be investigated further. Version 0 is compared to Version 1 and only changes desired should be the only differences. Otherwise, the Version 1 has problems. Same with comparing Version 1 and Version 2, only the differences desired should be the only differences. If code can run on different platforms and the code can give the same results.
Stress testing works great with testing maximum workloads.
Back testing compares different versions of modules. Especially, if they required reaction from stimulus such as individuals. Some situations may be life threatening. Some embedded systems such as a heart monitor cannot be tested against a live individual who is having a heart failure. These systems will have to be tested with stimulated data to depict an individual with a heart problem.