I do not know about deoxys, but you can get mew from a game on the wii from my Pokemon ranch. First you must get 999 Pokemon transferred from Pokemon diamond or pearl and you have to expand your ranch to reach there (taking 24 hours to build) then get an egg to trade with a person named Hayley on there to get the mew.
I recommend that if you have a mew from another event then do this as well so you can get a spare Pokemon you can use to bribe to get other mythical Pokemon.
And do this while you still can because my Pokemon ranch is a wii game that costs around $10 and you can get the game until january 30 2019 but you can only add the points to get the game from now until march 26th.
This video is how to make the construction go faster
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