Ben looks the same as he does in Alien Force/ Ultimate Alien because his appearance never changed during the events of Omniverse. Ben wears his green jacket, which has a stripe with the number 10 on it. He wears a plain black shirt and jeans. Ben also wears snickers. He continues to wear the Omnitrix on his left arm.
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Ben obtained the Omnitrix at age 10 when he was on a summer trip with his grandfather and cousin. He then used it to fight villains and such. When Ben was 15, after taking the Omnitrix off for a while, Ben puts it back on to find Max, which he does. He then uses it to end the Highbreed invasion. Ben defeated the likes of Aggregor, Diagon, and Malware when he was 16.
In The Dudesman Theory, Ben is still mad about Patelliday. He finds out that Rad Dudesman is the next target for the assassins, so he goes on a hunt to find him. He finds him, however, he dies. At the end of the episode, it is revealed that Rad is still alive.