There is no difference in chords, whether played on an electric, acoustic or classical. Most guitarists who play chords on an acoustic guitar usually try to play with open strings, and this is why...
No, they're all the same. Each string is tuned in the same manner. However, it may be found to be more difficult to play certain chords on an acoustic than an electric due to neck differences, but...
A chord is a combination of three or more notes that blend harmoniously when sounded together. A guitar chord is just the same except it's played on the guitar. Power chords only contain 2 notes but...