Free trial and payment questions

Hi

I have a few questions about the free trials, payments and coupons.

1. If a customer starts the free trial linked a subscription listing when do they pay? When they sign up or at the end of the free trial.
2. If they pay when they sign up if they cancel before the end of the trial are they automatically refunded?
3. If they entered a coupon code when they signed up and got a discount will that adjust the payment for 1 year or ongoing years? Or is there functionality to do both.
4. What is the best way of doing a member get member scheme – I.e if they sign someone else up they get both get a reduced price. I’m keen to make this as automated as possible.

Thanks so much in advance,

Kristina