Yes, it’s easy. Go to this page, purchase premium version and install it into your theme. Once activated the premium version, the free one will automatically be deactivated.
No, the premium version will keep in memory your settings besides unlocking new features.
The plugin works with all payment gateways that your WooCommerce supports: customers who click on the One-Click-Buy option will skip the Cart page and go directly to the payment page.
Yet, if you want that the One-Click-Buy button carries out the transaction immediately (so both Cart and Checkout steps are skipped), the only supported gateway for the moment is Stripe with our YITH Stripe (premium version). And, if the user has saved more than one card, it will charge on the default one.