Does this require an electrical outlet? Does it work up to 220 V input? How long is the cord?
Yes, you just need to plug it into a wall outlet and the alarm clock will work well, it work up to 220 V and the cord is about 3 feet long.
Can you set the clock to light up only - with no noise/sound?
Yes, just set the noise level to 0! It means the alarm wont make any sound.
Can you turn off the time display completely, and turn it on briefly in the middle of the night just to check the time?
Yes. Please press the setting button (in the lower right corner) to adjust the brightness of the time display or turn it off.
How to turn off the alarm?
You just push the button that you used to set the alarm.