FAQ: What is TurboTax Live?
https://ttlc.intuit.com/community/choosing-a-product/help/what-is-turbotax-live/01/27191
FAQ: How to connect with a live tax expert
https://ttlc.intuit.com/community/expert-review/help/how-do-i-connect-with-a-tax-expert-in-turbotax-...
FAQ: How do I schedule my review using TurboTax Live?
https://ttlc.intuit.com/community/expert-review/help/how-do-i-schedule-my-review-using-turbotax-live...
If you don't want that feature, then see this to remove it and go to regular Self-Employed Edition:
FAQ: How do I remove TurboTax Live?
https://ttlc.intuit.com/community/downgrading/help/how-do-i-remove-turbotax-live/01/27312
To cancel Full Service, you must go to the initial meeting and indicate that you no longer want the service or contact support directly.
Clear & Start Over will only work to downgrade products (like TTO Live to non-TTO Live, or Deluxe to Basic) but not to cancel Full Service.
See this TurboTax support FAQ on how to contact Support - https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-contact-turbotax/00/26991
To leave full service, click on "Leave Full Service" on the left bar. If you were on contact, the expert may have to disconnect before it ends. This will close your case and it will not be possible to resume from the point you were at with your expert.
If you are working in Assisted or DIY, and you entered unnecessary information that caused an upgrade, yes, use "Clear and Start Over" under Tax Tools on the left bar to reset your product SKU or go back to DIY from Assisted.