Downloadable products... handling versions

Hi, I am about to use Hikashop to sell software on my site. All the products I am selling are downloadable. I have two questions, both are in regards to how to handle releasing new versions of software that is sold on hikashop. I normally release new versions within 1 to 3 months, based on added new features or bug fixes. Here are my questions:

1. How do I handle new versions of a downloadable software product?
2. Is each version its own product?
3. If it is its own product, I would have to unpublish the old version. If I unpublish the old version from being displayed on the website, will users who previously purchased it still have access to it from their order details?
4. If I don't have to have a separate product for each new version, how else do I do it?
5. I already use characteristics and variants for products, since I have options for each product. However, is there a way to setup a test user with a test payment and test order number to see what the user will see once they make a purchase?

Thanks,
Michael