Constructed realities are so much fun. I'm with those who point out that the dream/simulation was just that- a simulated experience. How closely does it correspond to the world? How many of the "initial conditions" at the point of divergence, i.e. when the deam/sim was initialized, corresponded to real-world conditions?
For instance, I might have "dreamed" the Bill Gates and Steve Jobs that we know, and wake up in a universe where Gates never held onto the rights to DOS and Jobs never left Apple to muck around with NeXT.
Having awoken from this dream, and finding myself to be 5 years old in the 80s again, it's anybody's guess whether my comparatively undeveloped brain will be able to cope with things. I might have trouble believing that the world I've woken up in isn't another sim/dream. Maybe I'd be able to give adults some stock or gambling advice. If I saw events play out as I recalled them having played out in the dream world, I would probably start recording what I "remembered" was still yet to come. Maybe I could stop something, maybe not. It's hard to imagine a minor having much chance of influencing the world; could I have stopped the Challenger disaster, or the bombings of the 90s, or the unpleasantness in the Balkans? Perhaps I would become some sort of Cassandra-esque mental patient, akin to Bruce Willis in 12 Monkeys.
But it's just as likely I'd wake up in a world which radically diverged from the dream and I'd be just a little wiser for it.
See Replay by Ken Grimwood for much deeper exploration of this theme.
Sidenote: this happened to me once... sort of. I woke up in the middle of the night and a pattern of light & shadows in my quarters looked (through my eyes, lidded heavily with sleep) like the light that came in through the doorway of my bedroom when I was a child. For a few moments, I was a 10 year old kid again, my parents were sleeping just a door away, and everything was alright. It's hard to express how deeply secure I felt for that moment- the intervening decade-plus were gone from my mind. No growing up, no responsibilities, none of the nastiness of the last decades. I was a little sad when I woke all the way up.