of course not. But the sun is somewhat special in the fact that it is a lone star, most stars exist as part of binary or tertiary systems and other multi star clusters.
You can't - it's exclusive to Pokémon XD - Gale of Darkness. If you're trying to get one to evolve Eevee into Espeon, the only way is to achieve a happiness level of 220 or above and level Eevee up...
It's only used in Pokemon gale of darkness, to evolve Eevee into espion, to my knowledge. I do know that since Pokemon diamond has a clock, that there is no need for this item to exist in that game.