how did the red miles reach the alpha kids' universe? does their universe exist within the same genesis frog that the beta kids did? if so, why did everyone have to travel so far through the furthest ring?

Alpha kids’ universe is in the same Genesis Frog as the Beta kids’.

As for why so long, John and Jade were travelling through an alternate dimension at a speed so fast that time slowed down, and The Meteor Crew were travelling through the Furthest Ring where time and space work differently and it’s incredibly difficult to navigate through.