To preface this solution, you can earn this achievement by just finishing the speedrun mode, THERE IS NO MIN TIME REQUIRED FOR THIS ACHIVEMENT
and it'll run you about 1-2 hours of playing. The rest of this solution is composed of tips and tricks that helped me achieve a sub 1 hour time. Before attempting the sub 1 hour run, just know that this game will VERY LIKELY CRASH DURING YOUR ATTEMPTS.
I believe there is a way to minimize your crashes by, as ironic as it may sound: slowing down a little bit. It appears that the game loads chunks of the level at a time and if you rush into a section that's not yet loaded then the game will crash and dashboard you (there are NO CHECKPOINTS in the Speedrun mode so that means restarting from the beginning).
For reference: my best time is 57:06 with a sum of best segments at 53:56. I did this without any Out Of Bounds skips so if you would rather do any skips I can't help you there. The tips that helped me go sonic fast are below:
1.)If you beat Nerve and then restart the speedrun in the next level you will have the Nerve Sword instead of the pipe for the first 2 levels, this sword will kill all the enemies in one slash. (I didn't do this glitch on my run but it would help shave off a few crucial seconds).
2.)After the 4th encounter in Creep's Nest, pause and buy the Power Slash attack, this shockwave will 1 hit EVERY enemy up except for the bosses and cyborgs. Keep in mind the shockwave does use up energy so you need to manage it wisely. Energy will get used on the chargeup regardless of if you use it or cancel it
3.)Find a 2-handed weapon for when you are fighting the bosses, the spin attack can get MULTIPLE hits off on the bosses and can finish them off in as quickly as 2 spin attacks after upgrades if you angle it right. This will require a little bit of practice to get the hitboxes lined up right and is always a little finicky in my experiences but still much faster than just shooting them.
4.)Ensure that you pick up the Vis Carver and set it as your dropbox weapon, the damage on it is insane and i've found it to have a more consistent hitbox than any of the other 2-handed weapons.
5.)You can use Overload powered to level 2 to get unlimited sprints (at the cost of energy). This will shave off a few seconds each time you use it but I found it messed with the games' loading mechanic so I ended up not using it on my 57' run.
6.)If you use Electra you can stunlock the final Trafficking boss fight indefinitely and just dropbox a new one each time you're about to run out, this is MUCH safer than trying to kill him with 2 handed spins but is also slower.
7.)With the angel fights, you can two-handed spin to knock out most of it's health and then right before they shoot out the cores, spam the grenade to blow them up in the air, at best I would get all 3 cores and at worst I would still get at least 1 making it easier to dash and get the other ones destroyed.
8.)Disable Ruiner Kills, this will make the waves of enemies appear faster but has a downside of being more dangerous since you can't restock health/energy as often. (You can always pause and enable it in the settings if you desperately need it!)
9.)Pausing stops the timer so use this to your advantage to respec each time you finish a fight to maximize your dashes and vice versa to maximize your lethality in fights.
10.)On mother fights you can spam grenades if you get close enough to her to bring down the health faster. You can also save a few seconds by just tanking damage and dashing through her beam instead of activating your shield to block it but that is obviously riskier.
Alot of these tips, and a little more info on OOB can be found here: https://steamcommunity.com/app/464060/discussions/0/16217249...
Video of a 53 minute run for those who are visual learners: https://www.youtube.com/watch?time_continue=5&v=SD-R0jzD...