Special thanks for improved level solutions:
Bear19
Bloupeuh
Senen

To make the inputs easier
Left : = WASD (Input with left hand)
Right: = Arrow Keys (Input with right hand)

All inputs are displayed as U D L R
U = UP
D = DOWN
L = LEFT
R = RIGHT

When the sound cue for a cut arm is playing, wait for it to finish before moving again.

By following this guide completely, all achievements should unlock along the way, this includes:
Level 10: Spare an Arm
Level 11: It's a Feature, Not a Bug!
Level 18: Use the Box

As the solutions for these levels cover the level specific goals.

When loading into the first level. Press TAB then select Speedrun Mode.
This will make it possible to get all achievements in one playthrough.
(Just don't quit out of the game, it will not save progress)
Missable achievements are also covered, and will unlock if the inputs are followed exactly.
The time to beat is 600 seconds and only counts when in a level, so there's time to relax between each level.
I managed to get 477 seconds.
Good luck!

0
Left : URRRD DLDDR
Right: ULLLD DRDDL LLL

1
Right: LLDUL LLL
Left : R

2
Right: LLLL
Left : RRRRUR

3
Left : DRDRR DDUUL
Right: ULLDD DDLLU LULDU RDLL

4
Right: ULDUR DLDUD LL

5
Left : LUUL
Right: RRUUU ULLLR RRDD
Left : RRRRU ULLLR RRDDL LLUUL LRRDD RRRRR
Right: L

6
Right: LUU
Left : RRDDD DD
Right: DU
Left : RRDDD LL
Right: DDLLL
Left : RRDDD R

7
Right: LD
Left : RRRRR
Right: ULLLU UDDLL
Left : RRDDR

8
Left : LULLD LL
Right: RR
Left : RRURR DLLLR RDDDR
Right: L

9
Right: L
Left : RRR
Right: RDDDD LUDRU LUUDD
Left : RRRR

10
Right: RULRD LUUUU
Left : UUUUD DDLL
Right: DDLDU RDDLL LLLRR R
Left : RRDRR ULRDL ULLRR RR
Right: LL

11
Right: UUU
Left : DRRRR DDLLL L
Right: DU
Left : DRRRU URRR
Right: L

12
Right: D
Left : RRR
Right: UD
Left : RRR
Right: ULLLU
Left : DDD
Right: UUDDD LL
Left : UR

13
Left : L
Right: LL
Left : RU
Right: UURUU LLLLD

14
Left : D
Right: LLLDL LU
Left : URURD UL
Right: UUUUL LL
Left : DRRRR ULRDL ULLRR RR
Right: UUUUL

15
Right: URRDD LDURU ULLD
Left : DRRRU DL
Right: RRDDL LDL

16
Left : L
Right: ULLLU U
Left : RUUUU RRRRD LRULD LRULL LDDDD L
Right: ULLLU U
Left : RL
Right: ULLLU U
Left : RUUUU RRRLD RLULL DRLDD DDRRR R
Right: DLL

17
Right: ULLLD
Left : DRRRU U
Right: RRRDD DLDDL L
Left : LLLDD DRRRR R

18
Left : UUUR
Right: DDULL LLLDD RRRRR LLLLL UURRR RRDDD DLLLL UDRRR RUULL DULLL LRRDD RRRRL LLLLL LL
Left : LDDDD DRR

19
Left : RR
Right: DDDDD L
Left : LR
Right: LLDDL L
Left : LLULU UURRD DDUUU LLDDD RDRUU URRUU RR

20
Left : DDRRR LLLRR R
Right: LLL

21
Left : R
Right: LLDLL LLRRR RURRD DDLLD LUL
Left : RDRRR R
Right: L
Left : LLLLU LLDDD RRRLD RLULL UUURR URRRR RR
Right: LUL

22
Right: DLLL
Left : DULL
Right: UULLL
Left : RUUUD DDRRU RR
Right: UUL

23
Left : ULLDD RDRRR UDLLL ULUUR UURRR RRRD
Right: RRRU

24
Right: DLLLL LL
Left : RRRU
Right: RLRL
Left : RRRUD LLL
Right: RRLRR RLRRR UULLL LL
Left : RR

25
Left : UURDU LDDRU U
Right: LDDLL L
Left : DDRRR RRRLL LLLLU UDDRR RRRR
Right: LLL

26
Left : LLDDL LRRUU RR
Right: DDRRU DLLUU LLLRR RRRR
Left : UURRR RRRRL L
Right: UUDDL LL
Left : DULLL LLDLL DDRDR R
Right: DLLLL

27
Right: URRRR RDLRU RRRDL LRRUL LLLLL LLLUL URRRR LLLLD RDRRR RRDRL ULLD
Left : RRR
Right: URRDL RU
Left : RRRR
Right: RRRDL LRRUR RRUUU LDURD DDLLL LLDRR RRRUU ULDUR DDLLL RRRDL LLLLU LLDRR RRULL RRDLL URRRR DLLRR UUULL L
Left : RR

28
Right: RUR
Left : LULDD D
Right: LDLLD LUDRR DLRUL URRDR U
Left : UUURD RRDRU D
Right: DD
Left : LULLL DRRRL LLDDD RRRRR R
Right: DDLLL LL

29
Left : DRDD
Right: URRRR
Left : U
Right: LDDLL
Left : RDU
Right: LLULL L
Left : UUDDL ULULL UUURR RRRR
Right: DURRR UUULL LLL

Thanks for viewing this guide!
I would love to know what you thought about the game or this guide, comment below.
For my other guides, they are here:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2880052179