I would think the trial starts when you first run the apps and they record the fact they’ve been run and that starts the counter. If your OS version is stopping the apps from starting up and recording that they have then maybe you’ll be ok. But if the trial has actually started I doubt you’d be able to get the trial period reset.
If you've got the wrong OS then you would normally not be able to install the software. Is that the case for you?
Trials start counting down from first launch. If you have not launched then the countdown has not started.