Answer 1

There is no guarantee it will be shiny. The chance is the same as usual, 1/8192, unless the Ditto and other Pokemon are from different-language games (e.g. Japanese and English) then the chances are increased a bit.

Answer 2

No you can only obtain shinies in the wild or breed Masuda method.(a pokemon from a different country and your own)

Comments

i dont see why it was downvoted this answer is fine and technically still right

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I didn't vote this down but you don't have to use mesuda method to get shiny. Normal breeding can also give you shinies

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in heart gold I caught a shiny Pidgey.

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Cool story bro.
I caught a Shiny Patrat.

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I randomly found/caught a shiny pidove in Black 2 at Floccesy Ranch. I was so pround and happy. I didn't know what to nickname her though so I randomly named it Sparkles. lol