You can take the program for a test drive at any time, usually for 30 days (depending on the program). When you first download it, it has feature restrictions. Start the test drive at any time.
For the duration of the test drive it is completely unlocked, exactly as it will be when you purchase it. After the test drive is over, it reverts to the original feature restrictions. If you need another test drive, e.g. to evaluate a new feature - just contact me and I'll supply another one.