As far as resetting smoke detectors, I know of no code telling you how to reset a smoke detector. Resetting is really up to the manufacturer.
However, when a smoke detector goes into alarm (I'm not talking about supervisory), it latches into alarm requiring reset, and at the same time causes the control panel to latch into alarm, also requiring reset. If the smoke detector is reset locally at the smoke detector, but the panel does not reset, the panel stays in alarm.
For test purposes, the first detector sets the panel into alarm, but the next detector tested will not set the panel into alarm because the panel is still in alarm. If you are testing just the smoke detectors and want to know whether they activate with a magnet, the use of magnets setting off and resetting the smoke detector is just fine.
If, however, you want to know if the smoke detector detects smoke, and how the panel responds when the smoke detector detects smoke, you test the detector with smoke (fires don't carry magnets) and reset the panel between each smoke detector tested.