What happened to the Flash, when he entered the Marvel universe?

There Is The Marvel Comics Character“buried Alien” Character Which Is Implied To Be The Barry Allen Flash After He Seemingly Died Saving The Multiverse In Crisis On Infinite Earths(shown Below), But There Is Also An Instant In The JLA/Avengers Crossover. Flash Teleports Into The Marvel Universe And Sees A Mob Chasing A Mutant. He Attempts To Save The Mutant But Discovers That, Since There Is No Speed Force(where Flash Get This Powers), He Has No Speed And Is Beaten By The Mob. The Justice League Then Build A Device That Allows Him To Maintain His Powers. As The Device Was Not Justifying The Level Of Powers Which Flash Has And Because Of Which, He Is At First Caught Off By Quicksilver As He Was Not Expecting Him When He Was Ambushed, He Is Shown To Be Much Faster Than Quicksilver, As Quicksilver Is Not Fast Enough To Reach The Speed Force.