Uses the explorer kit and go underground. Just keep digging normally and eventually you'll find one. It does not matter where you go down.
you can't
Route 212 http://bulbapedia.bulbagarden.net/wiki/TM11
yes
152 is rotom.
An event
You can't, you have to Migrate him over or trade.
You can't catch Mewtwo in-game in Pokemon Diamond.
It is impossable to get one in Pokemon diamond,but there might be one in Pokemon platinom...... hope that helped!
Root Fossil Claw Fossil Helix Fossil Dome Fossil Old Amber Armor Fossil Skull Fossil Rare Bone
Golbat uses mean look in Pokemon pearl but i am not sure about Pokemon diamond and pearl.
Barboach. You can get it in the Safari Zone/ Great Marsh.
Yes the fossil is the skull fossil.