Morytania legs 2 are a reward for completing all the medium Morytania achievements. Once players complete the tasks, they can get the leggings by speaking to Robin in Port Phasmatys. They will automatically replace your Morytania legs 1, and they will be placed in your inventory even if your first set of legs was in your bank.
The slime pit teleport originally placed the player in the slime pit one level above the pool of slime itself and opposite the final stairs to the pool. A hidden update changed this to place the player exactly at the edge of the pool.
When smithing cannonballs, the estimate of time remaining in the progress dialogue doesn't take account of the speed boost from the legs.