Q 1 )Where can I find a light ball (Pls don't tell me I will have to catch infinite pikas for it) Q 2 )Is it that only pikachu or Raichu or Pichu can learn it or there are others Q 3 )Is using light ball the only option for volt tackle
I'm gonna have to tell you that you have to fight random Pikachu's to get a light ball. Depending on the game, Pikachu's have a 1% or 5% to hold one. If you are playing SoulSilver/HeartGold, then you can use Thief and takes Red's light ball.
The Pichu evolutionary line are the only one's that are capable of learning Volt Tackle. However, Smeargle can learn it as well if Volt Tackle is used against him and it uses Sketch.
Light Ball and Volt tackle have no relation with each other, other than Pikachu and breeding. You can use Volt Tackle without a Light Ball (ex: Choice Band Raichu with Volt Tackle), or you can use a Light Ball on Pikachu without Volt Tackle, though not recommended.