You cannot save a Pokemon game during a battle.
You get someones friend code -Pokemon Master
Of course you can. I played my Pokemon Diamond with my cousin that has Pearl.
You have to do single battles
so you can have double wild battles in the
yes garatina
You have to win 100 battles in the battle tower
on youtube
no
yes my brother said he saved it
You can only save one.
Unlike past Pokemon games, you have to delete you existing save file before you can save a new game. You can do that by holding Up+Select+B on the title screen (where it says Pokemon Diamond or Pokemon Pearl) Deleting the save takes a minute or two
no you already gave the manaphy egg away to your previous save