I heard that in one of them that you cant trade the Pokemon to anyone.
Which one can my friend do so the Pokemon is able to trade?
RNG is used to obtain shiny Pokemon/pokemon with perfect IVs and such. And Pokecheck is used to checks Pokemon's stats.
Source RNG: http://bulbapedia.bulbagarden.net/wiki/Pseudorandom_number_generation_in_Pokémon
Source Pokecheck: https://www.pokecheck.org/
And for trading you would have to use RNG and not Pokecheck because Pokecheck just checks the stats.
Hope I helped!