These TCG rulings were issued by Upper Deck Entertainment and have since been deemed unofficial by Konami. They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: 
If your opponent activates "Amazoness Archers" when your selected Level 7 Spellcaster-Type monster attacks, only the Level 7 Spellcaster-Type monster can attack because of "Diffusion Wave-Motion"'s effect, so your other monsters do not attack, but the -500 ATK effect of "Amazoness Archers" is still applied to all of your monsters.
After you activate "Diffusion Wave-Motion", if all monsters on your opponent's side of the field are destroyed (with "Raigeki", etc.) then your selected Level 7 Spellcaster-Type monster can attack your opponent's Life Points directly.
Your Level 7 Spellcaster-Type monster selected with "Diffusion Wave-Motion" must attack each monster on your opponent's side of the field, 1 at a time.
If your Level 7 Spellcaster-Type monster selected with "Diffusion Wave-Motion" has 1 of its attacks negated by "Magic Cylinder", that attack is negated but your Level 7 Spellcaster-Type monster still attacks everything else.
You can activate "Injection Fairy Lily"'s effect when she is attacked by a Level 7 Spellcaster-Type monster selected with "Diffusion Wave-Motion" because her effect is applied during damage calculation.