Using laptop while charging?

Yes, the laptop is normal usable while charging, it doesn't has to be turned off while charging, the battery doesn't damage while charging and using the laptop at same time.

the power supply that comes with a laptop usualy has only a very little power and can be overstress and heat up to much when having to run the laptop and charge the battery at same time, at least that powersupply should then be in the open for the heat to dissipate more to keep cooler.

Yes, you can use it.

You can use the notebook while it's charging or not, just make sure to fully discharge the battery and fully charge it from time-to-time for battery recalibration.

Are you really this dumb? Really?