Is the Mid-Ocean Ridge is the shortest chain of mountains in the world that extends along the sea floor into all the Earth's oceans

False.

Explanation:

The Mid-Ocean ridge is the largest chain of mountains in the world. The majority of it is underwater. It forms due to the movement of the different tectonic plates in the world, which allows the raising and solidification of magma where the plates diverge from each other, creating the ridge.

As it forms where the plates diverge, which is in several places on Earth,  it extends along the seafloor into all the Earth's oceans.