You can't You can't
You can find a dustox in eterna forest and there is also a trainer with dustox there too.
You are able to get Dustox by evolving Cascoon. Wurmple-Silcoon-Beautifly Wurmple-Cascoon-Dustox
you can find it in the survival area
Dustox is a Poison and Bug type pokemon.
Dustox can be found in Eterna Forest. it can also be found by battling these two bug catchers
Dustox doesn't evolve into any other Pokemon.
Entei can be found in Nimbasa City in Pokemon Indigo.
you will have to evolve it from cascoon starting at lvl 10
Yes, there is every Pokemon on Indigo. The easiest way to find Pokemon is to go to the ROOMS.
I doubt you will find Giratina on Pokemon indigo as it is not a generation 1 Pokemon (it isn't one of the first 151 Pokemon species)
The Pokemon cascoon will evolve into Dustox at level 10 =D
Dustox.