Using a 12v 600ma source is allowing 12 volts and 600 amps of power. If the device requires a 12v 500ma source, the larger source is acceptable. Please note that it will only be drawing on 500ma of the available 600ma.
You can use any 9v adapter as long as the output amperage is rated higher than the amperage rating of your appliance so yes a 600ma adapter can be used to power a 500ma or 400ma appliance
i am not sure, BUT according to the answer in this post:Can_you_use_a_9V_600mA_adapter_on_a_9V_400ma_scanneryou need an adaptor of 9v and AT LEAST 500mA (assuming that the appliance draws 500mA)
yes this will work fine
Almost certainly.
Yes you can. It will just take a little longer to complete the charge cycle.
yes, if the other adapter is a va
A: Disregarding the fact of different voltages there is the power to be concerned 9v x 1A = 9W, 15V X .8 = 12W. THE DEVICE WILL BE UNDER POWER.
As long as the batteries are putting out the exact same voltage, then yes you can use a battery with a higher ma rating.
Yes you can. But it may damage your computers power supply.
Yes. The current rating should be the same or greater than the original. This means the adapter can supply up to 500mA; In your case it only needs to supply 200mA, so it is more than up to the job.
Yes. As long as the voltage is the same which it is. The 800mA is the capacity that the transformer can produce safely without going into an overload state. Your original adapter was rated at 500mA which means that what ever device was plugged into it draws less that 500mA. You might notice that the new adapter is slightly physically larger. So you are safe to use the new adapter with the higher rating.