1. If you are on tps only, you are still legal to stay and work on USA. However, you have to reinstate your F1 status before you can change your status to h1b or green card. In other words, you cannot change from tps to any other status directly without reinstate to F1. 2. Parallel tps and F1 makes very little sense because you cannot use tps ead If you want to maintain F1 status. Tps is only a backup in some rare worst case scenario if you somehow lost F1 status, you still are legal because also had parallel tps.