The only move that it can learn is transform.
yes It can learn taun and transform
Only transform
The only move a Ditto can learn is Transform. However, when it transforms into an opponent, it will have the use of that Pokemon's moves for the period of the transformation.
Over the versions, the moves Gengar could learn have changed. As of the current version, and through leveling, Gengar can learn Shadow Punch, Payback, Shadow Ball, Dream Eater, Dark Pulse, Destiny Bond, Hex, and Nightmare.
To make Ditto transform, which can only be done in fights, just use the move transform and you will get the opponent's PokeMon with it's moves.
Transform. 10 PP Then whatever moves the transformed Pokemon has (Only 5 PP of each move though)
If they are not level 100, they have the ability to level up and learn moves that you don't want your Pokemon to know. My advice is that you keep your Pokemon with you. You can keep a Ditto in there if you want because Ditto cannot learn any other moves beside Transform.
Here are opinions and answers from FAQ Farmers: * Smeragle and Ditto can both be found in Emerald. However, these Pokemon (in the old games had no limitations) can learn moves from one another, causing moves being learned that should not be learned. * In the newer games, Smeragle cannot learn Transform and Ditto cannot use Sketch (it will always fail).
only transform. it cannot use any moves and HM/TM's
The only move it can do is "Transform" This means it can momentarily learn all the moves of one of the opponent's Pokemon, for example if you were battling a fire type Chimchar, it would learn some fire type moves. If you're looking for a Pokemon which always knows moves i would recommend catching another Pokemon!
To learn moves you forgot or didn't learn(exept TM & hm)
Not using him