Regarding gamma and chromatic calibration

Using the monitor center, I have performed gamma and the chromatic calibration using the PR-655 spectroradiometer. Please find below a few of my concerns.

While coding for making the stimulus, is it necessary to mention again the gamma value we need? As per the manual, in visual.Window, we have “gamma” properties, which we can set to the desired value.

For our monitor, I have performed calibration at different times. How do I mention which particular calibration to use while creating the stimuli? Or does it always take the most recent calibration by default?

I could detect PR-655 on the Mac to perform the calibration. However, during the calibration for the secondary monitor, the central spot of the calibration window always gets shifted to one corner in the extended mode. I had mirrored my primary display to get this to work. Is that okay?

Finally, I would appreciate it very much if anyone can provide me the driver files for making the PR-655 work on my windows.