Amazon Vine Experience

Can anyone share their Vine enrolment please?

1. Does it improve your sales?
2. Does the redeem units consider sales that leads to improving ranking? (Since it appears on manage orders page [i know the item subtotal is 0])
3. Do they charge us FBA Fees and Selling Fees for the units claim?

Last but not least, why do we need to pay the Enrolment fees when we are giving away free products?
As far as i know, not all of them are going to give revievvs. They just claim free products anyway.
If they are obligated to give revievv for each product they claim, i don’t mind paying for the enrolment fees. (Has to misspell the word revievv be allowed to post this)