What? Wrong. If the boy never grew into a man then Walter never crossed over and kidnapped him. If he did cross over and kidnap him, how did he die as a child? What you said makes no sense and what I said wasn't addressed by those two statements. If Peter died in Walternate's world as a child then Walter never crossed over and kidnapped him and none of these events started unfolding. And even if somehow Walter crossed over, kidnapped him, and Peter died in a car accident 3 days later, there was still nobody to use that enormous machine that they are keeping in that government facility, so there is no reason for that machine to exist. It really makes 0 sense. But I'm not even stressing it, I'm still a fan of the show and I'll let it slide.
Without Adult Peter future Walter/Olivia/Astrid would send the machine back in time to be activated by someone else besides Peter. Remeber back to last season they said Walter had sent the machine back in time and the team had disbursed the parts between the two universes. The reason it was between both was that Peter had originally decided to save one universe and the result is what he saw in the "future" episode last year. After seeing that future he decided to change things up and bridge the two universes thus changing the future he had seen. They also mentioned that they were getting readings from the hole the machine created as well as the parts that lead them to the time travel bit.
I think a lot of people a getting caught up on things that have changed because adult Peter never existed. It's almost like a reset but this time all f the events happened without adult Peter in them (from either side). Walter and Walternate would have crossed over into a different universe regardless of what happened with child Peter. Walter just pushed the time table up for crossing up when he saw what he saw with his mirror into the reverse.
Without adult Peter there is no anchor for Walter to become normalized as we have come to know him. Think back to season 1 and the journey his character has taken. Also without adult Peter they need to keep him under lock and key as there is no one to check him out. Think back to season 1 with Olivia without adult Peter she remains the cold almost emotionless person that we were introduced to. Astrid as well, without adult Peter she takes a larger role in the team instead of staying back and being Walters a.ssistant.
Also, we have only gotten through one episode. This will be a season long arch (IMO). Give them time to flesh it out Nd give answers. I have only replied with what makes sense to me from watching from season 1. If anything this show requires you to know what has already happened Nd will continue to draw on past seasons.
The basic premise is that everything happened the same over the past 3 years, they just happened without Adult Peter. A telling sign that the "erasing" was not complete is Peter leaking back into this universe and Walter saying he hasn't felt right ever since they used the machine ;).
Think to season 1 as well when Walter explains multiverses. For every decision wew make there is another universe where we made a different decision. We are almost in a new blended universe which would also explain the new yellow/orange/amber intro.