I tried to write Inception backwards but ultimately failed. Time to ice my brain.
A team of people give codes to a poor man outright, and he buries them many layers deep within his subconscious, making it second nature to him.
I tried what I could.
A man spins a top, moments before leaving home for a long flight on which he falls into an incredibly deep sleep, pulling an asian CEO into the dreamworld with him and aging him horribly in the process. There he goes for a swim, and wakes up in a crumbling city where a pretty young girl has also been pulled into his dreams along with the son of a dying owner of a major corporation. They walk for a bit, and then slowly begin to wake up by traveling to a snow-world where soldiers race around backwards on snowmobiles. They take steps to repair a vault door, with the aid of an english con-artist, a chemist, and the man's partner (who is also the girl's current boyfriend). After this the group travels to a hotel, where they wander around a bit in ever-shifting gravity before it's finally restored. During this time the man and the son of the mogul chase security around for a bit, and the girl and her boyfriend slowly grow apart. Eventually, they escape to the rainy city streets where they have a car chase and the asian CEO's sanity and youth is restored when a dream-soldier symbolically uses his gun to pull a bullet from his chest.
The man then wakes up to find himself on the plain, landing in London. The group performs some experiments in a warehouse, until the girl finally returns to her college studies at Oxford. The Chemist returns to his usual job of helping people sleep, the con artist travels with him, and the psychologist and the man head to south america where they use what they've learned to help someone relive his memories of a riot that took place during his childhood.