1. A huge difference if used properly
2. You feel far more energised while on them, so yes you can train harder for longer. You can also add extra sessions due to the fact that AAS's work by increasing the rate of recovery in your body. This is usually not recommended though, as injuries are easily obtained if you overdo it (due to the fact that fatigue signs are harder to perceive)
3. Strength gains are quick and somewhat permanent if you continue to train heavy after AAS usage (there is a noticeable drop-off post cycle though)
4. Definitely. Appetite just about doubles
5. Not at all. Most educated AAS users (usually the guys with 6 packs as you're referring to) are just as serious, if not more serious about their diet than the rest of us, due to the fact that the better their diet is on cycle, the cleaner their gains will be (although this obviously doesn't differ in common sense whether using AAS's or not.)