The timeline/AU of this verse
Steven is champion for 3 years and on going. He has a passion for exploring and battling and doesn't have much interest in running the Devon corporation, but he is the biggest supporter of his father and the corp.
Though he is 18, the plot of Alpha Sapphire still does occur. He meets Orlando, May, and Wally and assists them on their journey frequently. The events have very recently been resolved.
He has not been challenged for his position by the trio yet (and out of the three, Wally is the most likely to challenge him).
May and Orlando become pokemon rangers, though in the distant future, May intends to succeed her father as the next in line Professor through her experiences and growth as a ranger.
Wallace(21) is a little more like his Anime counterpart, though he is still a fearsome Gym leader. *Lisia is 13 and still his niece. He and Steven are still very close friends.
Steven bonded the most with Orlando(16), while May(16) bonded most with Wally(14). However, the three are all good friends.
The only other region Steven has been to thusfar is Johto at the age of 16. There he met Ethan and Lyra. He gave him a Beldum and Lyra a a Mudkip. He also met Cynthia during that trip.
In this timeline, Hoenn has a historic relationship with Kalos, hence mega stones being scattered through the region and it not being a foreign concept to him or researchers/serious trainers.
Though he had Metagross(Campbell) as a Beldum since he was 6, he did not begin to battle with him until he was 14, and achieved mega evolution with Camp at 16 when he almost lost his position as champion. The two were intensely synched for it to happen then. He cannot mega evolve his Metagross on a whim just yet like Orlando can, he and his Metagross, though strong, haven't reached the maturity for it to come on command yet. **Neither has Orlando, but Orlando is very fiery and emotionally driven. He is a bigger battler at heart.
In this timeline/universe, on average, trainers set out on their journies at 14, the exception to this is Red, Green, Ethan, and May. All because the four were agents of professors.