Customer Reviews Option only for Items Already Bought

Hello. I am a newbie website owner. I wanted to setup my site so that customers can write reviews only for items that they have bought already, not for any other. The reason is that I plan on giving Reward Points to customers for writing reviews, good or bad. I dont want customers randomly writing inauthentic reviews in order to avail the reward points.

My other issue is that I have Product packs on my website. A customer can buy 3 flavors samples from a drop down list. I would want the customer to be able to write reviews on the specific 3 flavors that they bought, not for the sample pack as a whole. Can this be done?

I would really appreciate any help in this matter. Thanks guys.

Atif