As per my understanding your qeations are related to Magento platform features(Whether they exist or not).
1) You can try with Magento Downloadable products. You can restrict number of time a user is allowed to download the product. You can also allow the user to download the sample of the eBook.
2) Magento allows shopping cart rules as well as catalog price rules. Please Shopping Cart Price Rules
3) To contact Magento please visit https://magento.com/contact-us