Hi,
- As far as I know, Stripe should notify WooCommerce about the cancelled payment and the order will be marked as Canceled or Refunded automatically (you can try testing this with Stripe sandbox for developers).
- Unfortunately there’s no such option, but it may be possible with Requests, if you enable personal requests then users can make a private request to the vendor, and vendor can reply with an offer. Then user can proceed and pay for the offer, this creates a new order in the same way as with purchasing listings.