question

To address your main two questions:

• A 17.0 license, regardless of its maintenance expiration date, can license any bugfix release in the 17.0 feature release branch (ie, 17.0.0, 17.0.1, 17.0.2, etc).
• A model built in 17.0.x can be opened in 17.0.y - model compatibility does not change across bugfix releases in the same feature release branch.

Your customer using 17.0.0 should upgrade to the latest bugfix on the 17.0 branch, which at this time is 17.0.4. There is almost never a reason to use an older bugfix version on the same feature branch (ie, don't use 17.0.3 once 17.0.4 is available). As mentioned above, their expired 17.0 license will continue to license all bugfix releases on the 17.0 feature release branch (which, by the way, is the Long Term Stable branch, and will receive bugfixes throughout the year).

That said, you can install multiple versions of the same feature release branch (ie, 17.0.0, 17.0.1, 17.0.2, 17.0.3, 17.0.4, can all be installed simultaneously on one PC) by following this procedure:

1. Install FlexSim 17.0.0
2. Start FlexSim 17.0.0 one time
3. Close FlexSim 17.0.0
4. Copy the entire program directory (typically "C:\Program Files\FlexSim 2017"), to a new location (for instance, "C:\FlexSim\FlexSim17.0.0")
5. Edit the file (example path as used above) C:\FlexSim\FlexSim17.0.0\program\productid.txt - add the bugfix release number to line 1 (ie change "FlexSim17.0" to "FlexSim17.0.0")
6. Right-click the file (example path as used above) C:\FlexSim\FlexSim17.0.0\program\flexsim.exe, choose Create shortcut.
7. Move the newly created flexsim.exe - Shortcut file to your desktop, or some other convenient location. Rename it with a more useful/descriptive name, like FlexSim 17.0.0.
8. Repeat above steps for any 17.0.x bugfix releases that you want installed simultaneously on the same PC. If you install them in order, then each new installation will upgrade the previous one and you won't have any problems. If you installed 17.0.4 first, then in order to install older bugfix releases in that feature branch you will need to first uninstall 17.0.4.

Again, there is almost never a reason to use an older bugfix version on the same feature branch (ie, don't use 17.0.3 once 17.0.4 is available), and most users will never need to maintain multiple bugfix versions of the same release branch at the same time.