It is possible, but you need to be very careful. Discuss any exercise plan with your doctor before starting. You might also want to meet with a personal trainer.
You can exercise with sponylolisthesis. Depending on the severity, no limitations to limited general exercise can be done. You should discuss your particular case with your doctor to determine the best type and amount of exercise.
Spondylolisthesis or Cervical Spondylosis is a painful situation. But can do exercise after consulting your doctor. Exercises like pelvic tilt, knees-to-chest, back strech etc. are really good.