Like MecanoJilano said, you need to complete a small quest in Shoal Cave in Hoenn (north of Mossdeep City). You will need to find 14 diferent pieces , in which 7 of them can be found during low tide and the other 7 in high tide. You can check which tide it is based on the poketime through this link. Once you got all 14, talk to the NPC at the beggining of the cave and he will change the 14 pieces for a Shell Bell.
Yes it does :)
You can check what it does here. If in the future you want to know if a move is coded or not check the PvP rules, if the move is not in those lists it is coded.
Since both of your questions were answered I will lock the thread. Thank you MecanoJilano for helping us once again :y:
Best of luck and Merry Christmas :)
[glow=purple]Locked as Solved[/glow]