For the first time this guy appeared in the teaser of a new event in the Onrefni Adventure CH2. Then he appeared in Application 410.
The answer is in Application 410.
1) Maks is Mobile Hacker. As we remember from the ending of OA CH2, he was splitted into atoms. Dude didn't die... Who helped him to survive ? Probably Andrew Rox, because judging by the reaction of Adeon — he is not in the business.
2) Andrew Rox is The Guest, as you can see from the screenshot. If we assume that he was the initiator of this transformation, then why ?
In Rogue & Knight, Andrew is the father of the two main characters (rogue and knight — Kyle and Roger). It is an enemy, BUT one that does nothing. In the game, we play in a location that is unclear in the plot, in the sense that the description of the Rox family in the game itself simply does not connect with the gameplay, as I believe. If you take into account the gameplay in the story plan, it turns out this picture - Andrew could not make peace with his sons, because we know from the endings that he is responsible for their death. As a result, he could have joined forces with the MH to try again.
How does he know MH ? Andrew appears briefly in Onrefni Adventure Strange Stories #1.
"A man in a grey hoodie and purple trousers enters the room. He is holding a glass with a plant in one hand and a book in the other. " He is the Creator of creepy toys "lovely babies", one of which was at Nastya's. These toys he sells under the brand "Adeon's Circus of Fun" — so called circus of Adeon. And Adeon, in turn, knew the MH, by ARG in Nick's Discord. My guess is that Adeon might have told Andrew about it, given that it was essentially Andrew's childhood toy…