To address your questions in order:
-By default, when a buyer makes a sale, we send them one or more fully customizable email messages to confirm their order and deliver crucial information such as any download links or digital codes they'd purchased:
-When setting up a discount code, you can simply select the "Item Unit Price" option to apply a discount to a specific product:
-Your main Dashboard page will display your most sold products, as well as a list of your most recent transactions. You will also have your Transaction Log, which is a permanent record of your sales history, which can be exported in a tab-delimited .txt format, allowing you to import your records into a spreadsheet app of your choice for further record keeping and analytics.
There are additional sales tracking options outlined on the following Help page, with a few caveats explained in further detail on that page:
-We do offer several Help pages for sellers to guide them in assisting buyers that may encounter download issues. The most common issues are covered on the following pages:
Regarding your last question, we have no way to support recurring payments/subscriptions from buyers at this time. As explained in that thread, our links are mainly designed for one-shot purchases where the buyer pays and then claims their download.