The day after a visit that happened, the customer gets one thank-you email with five stars to tap. Each opens a review of that visit with those stars picked, where they can change them and add a few words if they want. Only someone who came can leave one, because the link is their own booking's, and each visit gets one review. No-shows and cancelled bookings are never asked.
Your booking page shows your stars and how many reviews you have under your name, from the first review, and the newest few with words under your services, with See all for the rest. A review shows the customer's first name and initial, the service, who did it and the month. Never their email or phone.
Under Shop settings, Reviews you see every review and your average, and you can reply to any of them. Your reply shows under it on your booking page. If a review is abusive or gives someone's personal details, you can hide its words, picking which of those two it was. The stars stay and still count in your average, and the page says the words were taken off, so hiding a review can never raise your score.
Under Shop settings, Reviews, you choose where reviews go: FullDiary, Google or Both. Both is the standard: once your Google review link is added there, every customer who leaves a review is offered their words to copy and a button to your Google review box, whatever stars they gave. FullDiary cannot post to Google for them: Google only takes a review from the customer's own Google account. With FullDiary nobody is sent to Google. With Google the thank-you email goes straight there, and your booking page shows no reviews.
Reviews are on for every shop. To stop asking, switch off Ask for reviews under Shop settings, Reviews: no thank-you email goes and your booking page shows none. Nothing is deleted. FullDiary does not copy reviews from another booking app, Google or anywhere else, because a review that did not come from a visit booked with you is not one we can stand behind.