In kingdom hearts2 what is silver Sora

There is no such as a silver Sora in KH2, or maybe you are talking about the drive form called Final Form. Because in final form Sora's clothes become all silver, so maybe that's the one you're talking about.

So this is what Final Form is: Final Form is the last drive form that Sora can get, you can only get experience for the form by killing Nobodies, and the special move you can get is Glide, where you can fly around, but you can't go up, only go forward without falling down much. You can get this form using any of the previously obtained forms. You must fit the following criteria to obtain this form:

- Have a total of 5 Drive Gauges
- Have activated the fight scene with Roxas and Sora
- You MUST be in battle when activating your drive form
- It can be obtained in ANY world after the fight scene

An easy way to obtain this form is to go to The World That Never Was and right after the fight Xigbar (dude with the gun I believe) Donald and Goofy will be walking around the area you defeated him in. Progress forward to Naught's Skyway, BUT DO NOT goto the next area. Transform into any desired form in a group of enemies, if you do not transform, head back to where Donald and Goofy are while in your drive form. Your drive will be maxed out again, and rinse, lather, repeat until you have the Final Form.

For those who've already gone past this point, head to where the Final door
to Kingdom Hearts lies(Xemnas Fight)All your friends will be standing around,
so leave back outside and use your drive form in a group of enemies. If you
fail to go into the Final Form, head back to where all your friends are, and
your drive gauge should be maxed out again. You must enter the door while in a
drive form.