Not typically. Spinal stenosis is a narrowing or pinching if the nerve canal, it can usually affect things spine related, but not really brain related.
Not lumbar. The meds you take for it may.
No. It will not.
No. Spinal stenosis is a diagnosis related to the spinal canal and the neural elements found within when there is too narrow a canal causing pressure on these neural structures and the brain is not one of those structures found outside its own bony cover, the skull's cranium.