Hi there!
Welcome to the board! You'll find tons of useful information here and good support. There is also an excellent search function on top of the page, where you can find lots of useful reading.

As for your questions:

1. As long as you drink your water (I'd recommend about a gallon a day) and don't substitute it for any other drinks, an occational Soda might be okay, IMO. Now, some people recommend against it, but I've had Diet Coke now and then without a problem. Maybe you would like to cut it out during Induction though, as this period is supposed to help weaning your tastebuds out of sweet things and stabilise your blood sugar (which for some people seem to be affected even by sugarfree stuff - as their bodies "expects" sugar carbs merely by feeling the sweet taste.)

2. Magnesium, potassium and calcium supplements are recommended. Magnesium deficiency, especially, lead to fatigue and muscle cramps.

3. That urine colour seems to be quite common while eating certain vitamins, according to lots of threads in this forum. I wouldn't worry about it.

Cheers!

/gil

EDIT: Taters beat me to it...