While it's a creature, Gruul War Plow has creature type Juggernaut. It doesn't have any abilities associated with the card named Juggernaut.

While it's a creature, Gruul War Plow gives itself trample.

A noncreature permanent that turns into a creature can attack, and its abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.