Welcome to Neuro Talk. I did a bit of research to find out what your MRi may be talking about. I am not a professional, just pretty good at looking up things. Developmentallly narrowed canal, may mean that you were born like this, and may be a "question" for your doctors.
The thickening of the interspinous ligament, is the ligament that really helps with flexion, "movement". Maybe it can be resolved with PT. You need to go over the results with your doctor for sure.
The rest really isn't so bad. Any time the MRI says "Mild" that isn't something to worry about surgery about. It is only when it says "severe" that you have an issue.
Try not to over do any excersises, until you get clearance from your Doctor.
I am hopeing that some PT may resolve the low back pain for you. Many back issues do get better.
Google up these words that are used in your MRI. " developmentally narrowed canal" and "thicking of the interspinous ligament". There are some really good articles about it. I wish you all the best. ginnie