This guide offers hints for unlocking all achievements.
Solving puzzles, mysteries, and challenges on your own is a core part of the game's experience, so I won’t provide step-by-step walkthroughs or direct solutions for each achievement.
Most hints are hidden behind [spoiler] tags. If there are multiple hints for a single achievement, the later hints provide more direct guidance.

The following achievements can be unlocked through normal progression in the game.

• You can unlock this by talking to Butter each time they appear in various areas along the way.
  
• Butter appears in the following areas: Belwheat Valley / Entrance Ruins / Forest Cavern / Port Naga / Basin 21 / Pastel Strata / Terminus

The following achievements can be unlocked by maximizing completion percentage.

• You can find hints for unlocking this achievement in two places.
  
• One is Pastel Strata, where three "tech" notes offer obfuscated clues about how to perform the "tech".
  
  • Hint: the notes do not mention all the requirements to perform the "tech".
    
  • Another hint: the "↑ + ↓" in the first note does not refer to bat swing directions.
• The other is Trial Terminal, located just after Precipice Bridge, which provides a clear explanation of how to perform the "tech".

• This "collectables" refers to the Train Ticket, Master Key, and Rollerblade.

• This can be unlocked in False Field.
  
• You need to be launched by the dog in False Field.

• Note that this cannot be unlocked by simply collecting all the required collectibles.
  
• After collecting them, you'll need to select the stamp option during a conversation with the receptionist at Heaven's Channel.
  
• You need one more item in addition to all the completed postcards.
  
• Specifically, it’s Butter's contact card.

• This can be unlocked at the Final Stats screen with 108% completion.

For more detailed information on maximizing completion percentage, refer to the following guide: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3398070185

• This achievement can be easily unlocked by speaking to creacher that appears in Belwheat Valley. You need to be launched by creacher.
  
• There's another way to unlock this achievement by speaking to an NPC in Port Naga. You can find them in the post office.

• This can be unlocked when thrown by an NPC other than creacher.
  
• Master throws you after a certain condition is met (specifically, collecting the fizzy on the small island to the left of Master).
  
• An NPC in Port Naga can also throws you, but this will not unlock the achievement.

• I'm not sure what counts as a "slam," but at the very least, you need to slam against walls and floors with a certain speed, causing the character sprite to become paper-thin after slamming.
  
• Note that you also need to slam against ceilings to unlock this achievement.

• Area 1 is Belwheat Valley.
  
• If you try unlocking this achievement fairly, you'll need to use up-swings to slightly gain height while jumping.

• FIC means Fizzy Ice Cream.
  
• It's possible to get the Fizzy in Belwheat Valley in under 1 minute with some practice.
  
• This achievement can also be unlocked by getting any Fizzy outside of Belwheat Valley.
  
• By the way, the respawn option on the pause screen is disabled right after starting a new game. What would happen if you trigger a respawn in this state…?

• There are hints in the game for this achievement, and the conditions can be easily inferred from them.
  
• One of the hints can be found in a note at Terminal Station.
  
• The other hint can be found in the note at the "???" warp zone.
  
• The "Delta" mentioned in a note refers to the speed baseline.
  
• One of the requirements to perform ILDM is a speed of 50 or greater. What would happen if it's performed with a speed of "Delta" or greater...?
  
• Reaching a speed of "Delta" is challenging but achievable. A good start point is the left edge of Precipice Bridge.
  
• I’m not sure if it will be helpful, but here’s the video of when I unlocked this achievement: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3406031812

• The "special effects" required for this achievement are Charge, Vector, and Float.
  
• There are few places to apply all special effects at the same time. This achievement's fun comes from finding them.
  
• Since Float is required, this achievement can clearly be unlocked in Villith’s Drain.
  
• It’s technically possible to meet the condition in just one puzzle room, but it’s quite challenging.
  
• But there is an easier way to meet the condition:
  
  • The Charge state can easily be maintained and carried over to another puzzle room.
    
  • There is a puzzle room in Villith’s Drain that contains both Vector blocks and Float blocks.
    
  • Conveniently, that room is near another puzzle room that contains Charge blocks.
    
  • After a certain setup, you can start applying all special effects in the second puzzle room from checkpoint 9.
    
  • In some cases, you need to go through the intended route in reverse.
    
  • To accomplish this, avoid warping to checkpoint 9 before starting to apply all special effects.

• It might seem impossible at first, but with enough practice, it’s absolutely achievable. Good luck!
  
• You can completely skip GC Warehouse.
  
• From Goldcherry Factory onward, there are no significant shortcuts, so you’ll need to progress fairly.

• This is a much harder version of Cereal, but once you've achieved Cereal, this is within reach with additional practice and route planning. Best of luck!
  
• The baseline is finishing the game in 1 hour or less with 100 or fewer deaths.
  
• You can skip Forest Cavern and Eroded Beach entirely by using the train.
  
• You can also skip more sections/areas. For example, Basin 21 checkpoint 7 serves as a great starting point.
  
• Actually, you don’t need extreme precision or special tricks to unlock this achievement. If you can calmly execute what you learned during a normal playthrough, it’s well within reach. For reference, here’s the video of when I unlocked this achievement:

For more details on how rank is calculated, refer to the following guide: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3400212896