In Pokemon lottery corner in every Pokemon game if ALL the digits of the lottery matches exactly in one of your Pokemon then you will get a masterball for a prize(it is very difficult though).
No.
you cant
There is only one masterball in yellow.
Sorry you can't
No.
You can only get another masterball if a friend trades you a Pokemon holding the masterball they obtained.
Lilycove lottery
From the Lottories.
you cant
You can get another masterball by winning the Goldenrod lottery.
I recommend trading a Pokemon from another games holding a masterball. If you don't understand. USE THE TRADED MASTERBALL!
Have it traded from another game.. that's about it