Yes you can, but it's really hard. If you duplicate Master Balls with the Missingno. Glitch, it's much easier. But I wouldn't recommend it if you like having un-glitched Hall Of Fame data.
grovile
Yes you can catch the three Legendary birds in Platinum but you'll have to beat the game first and to minor side activites before hand
nothing really
no
no.
try to catch your legendary. It varies on which legendary depending on what starter you chose.
after u get the national dex and catch dialga and palkia and the three lake Pokemon talk to oak in eterna and they apear on ur map
You can catch Articuno in the Seafoam islands (Kanto), Zapdos at the Power Plant (Kanto), and Moltres in Mt. Silver (Johto).
Because their supposed to do that. I watched Pokemon Platinum Walkthrogh by Super Skarmary. That's how to do it. Abbie and Jirachi.
Trade from Fire Red
The three legendary birds, moltres zapdos and articuno and mewtwo and one of the three legendary dogs depending on your starting Pokemon and deoxys
a utra ball or a master ball