You must have an auto right?
1. The power means it will change it down a gear for more torque, makes the car have a more aggressive feel and more torque. Also, it changes gears later in the rpm range.
The snow starts in 2nd gear for less torque, and keeps it in a lower rpm range, so it has less chance of wheel spin. Good for driving in muddy situations or snow.
So, you should have more torque in power mode and much less torque in snow mode.
2. As for the spoiler up and down button...to me it sounds pretty simple, but I have no knowledge of this in Skylines. If the button doesn't work maybe the motor for it is broken or your car has an aftermarket spoiler, which made the button obsolete. Who knows.
Please correct me if I am wrong people.
Hope this helped Justin.
Cheers.