#1
Which goes first in from guitar to amp: overdrive -> distortion pedal or distortion -> overdrive pedal? Consider I am using both pedals on my board.
#4
That really depends upon the type of pedal, the way you use them, and pretty much every other condition in the entire universe, including but not limited to the price of rice in China. Just try them all to see what you like. There's no right or wrong when it comes to tone.