Here is the full list of all 19 Highway Blossoms achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Completed Highway Blossoms on Extreme difficulty
Set the character speed below 10 characters per second
You know what you did
Tried out the hi-contrast textbox. Who knows, you might like it!
Checked out the guest art section. Now all it needs is a glass case.
Checked out the credits on your own time
Turned on Goofball Mode
Finished the epilogue
Finished the story
Got lucky at blackjack
Unlocked every journal entry
Now you're back on track
Let's hope you don't ever again
Didn't find the second piece of treasure
Found the first piece of treasure
Got a copy of the miner's journal
Started a new game
Turned on skip mode for all messages