That's what the designers wanted.
No, but a 45 wailmer is basically a wailord.
you can find it at rout 129
in shinetown city
You do not need a Wailord to catch a Registeel in Pokemon Emerald. You may need a Wailord or any other water-type Pokemon to surf to the place where you catch Registeel, but other than that, you don't need a Wailord.
wailord you have to evole from wailmer and relican you find in dive mode.
A haryama A blissey A Wailord
Evolve a Wailmer (Level 40)
Get a Wailmer and evolve it. It evolves into Wailord at level 45.
Wailord do not evolve any futher. They are the first and last evolution of Wailmer, who evolve into a Wailord on level 40.
You Can't
Swampert or Wailord.
In Pokemon Emerald to solve the Sealed Chamber puzzle you need to put Wailord at the top of your party. Relicanth needs to be at the bottom of your party. This order is the reverse of the order needed in Pokemon Ruby and Sapphire.