Thank you for connecting with the QuickBooks Community,admiralhouse. Yes, it is possible to have both versions running on the same computer as long as your computer has enough storage and meet the system requirements. However, if you are using the same company file for both programs, once data is entered into one, it will not be reflected in the other version. If it's two separate or different company files, then you do not have anything to worry about. It can be done.
For more information on downloading the 2020 version, this article is a resource fill with a video presentation and ways to prepare, install, and activate your program.
Please let me know if you have any other questions or need clarification. I will be around to help. Know that you are welcome here always if you need assistance. Take care.