no
this is impossible without cheating, even with cheating it may not be possible.
events
no
to get Manaphy without cheating, you have to have Pokemon Ranger, beat a certain mission, and then somehow transfer the Manaphy egg to Diamond or Pearl.
Only if you got the event.
You can't
You have to mete the Pokemon lots of time, 1 time it will be shine.
you can't
The Pokemon that can be caught without special events, trading, or cheating in Pokemon diamond are: Uxie Mesprit Azelf Dialga Giratina Heatran
you can get to all islands without events to get the three remaining legendaries are paticipating in an event not possible anymore or action replay, cheating and glitching with the game.
i know how to get nearly every Pokemon without a cheating device. do you know how to get Deoxis on emerald Or is there a way to get Darkrai on diamond without cheats?
You don't know?!It's Dialga of course!