Recurring payments with Paypal cancellation and continuation

Hi,
I'm working on creating a user registeration based on payments. Manual or recurring payments.

Just to confirm. To cancel a recurring payment the buyer or seller must go into paypal to cancel the recurring payment? There's no interface option for it with Gravity Forms right? except for the IPN triggering afterwards?

How would I go about allowing the buyer to change their recurring payment to a different package? Do I have to restart the recurring payments? If they still have days left on their membership, can the recurring payments only start when they run out? I read that it's possible to setup trial days, how do I put that into the form?

To allow a buyer to reactivate their subscription after it was cancelled they would need to recreate the subscription right? Therefore the seller would not be able to do it for the buyer?

Does authorise.net work the same way?

hi chris,
thank you for the response.

is it possible to create a form that would define the number of trial days based on a variable from the logged in user?
that way if there's a price change i can request users log in to update their subscription.

does the IPN trigger any hook when the subscription is cancelled?