Mrireadsc3-4 disc herniation stenosis with ap of 0.7cm? indention on spinal cord. is there risk with riding thrill rides at the fair or theme parks?

Potentially: 7mm is a relatively small area for the spinal cord. The spinal canal gets even smaller during hyperextension of the neck, and could potentially injure the spinal cord. So you would do well to avoid activities where extension of the neck might occur, as in riding a roller coaster or similar activity.

Yes! Big risk!: Those thrill rides will throw your head around, as your head is not really secured in the rides. This can cause either acute swelling of the herniated disc, or even a new herniation in a vulnerable cervical spine, which could result in either worsened radicular symptoms or even paralysis if it goes to far. You should not to go on these rides. Too risky!