I made a walkthrough over at GameFAQs here: https://gamefaqs.gamespot.com/pc/318337-dynopunk/faqs/80634
I don't plan on converting it here because it's gonna take a long time to do (there are a lot of tables), so I decided to just put the achievements here instead as a guide.

Obtained through story progression and can't be missed.

You're not there yet!

Ordered from the earliest to the last.

Persuasion skill upgraded
Save Justin from his boss's wrath


In day 1, when dealing the phone call from Justin's boss, choose "Accept", "This is the repair shop.", and "No".

Tea Rex
Offer Dysella some tea


Self-explanatory. The earliest you can get it is at day 1.

A bad son
Reject Mom's phonecall


Self-explanatory. The earliest you can get it is at day 1.

I love trouble
Bon smashed the window 5 times


Self-explanatory. The earliest you can get it is at day 2.

Bravehurt



Make sure you're friendly enough (->)[gamefaqs.gamespot.com] with Dysella to teach you how to do a middle finger in day 2, then do the actual middle finger at Bon in day 3.

I saved you
Talk Bon out of assaulting the city-hall


Keep Bon's mood on friendly (->) state. Make sure to convince him to become a cop at day 3 and 15 and convince him to not go to the city hall at day 19.

What bros do
Get smooched by Sid


There are 2 ways to unlock this:

• Keep Sid on romantic (<-) state, and on day 12, accept his kiss.
  
• Keep Sid on rock! (->) state, invite him to the party at day 20, and accept his kiss.

Dino for one
Have the dessert all by yourself


At day 15, choose "I'll have it with tea." when Mia offers you a cupcake.

420 D
420 D


Get exactly 420D. I did it in day 15. Spend your money to buy anything except the time machine part in day 8 to reset your money to 0. After that, choose all option that can net you money. Make sure to not choose any option that make you lose money (Lance, Marcus Trust at day 13).

Mission imPAWssible



Either accumulate 4 ❌ Mistake in day 17-19 or simply reply with "It's none of your business." after you repair/break the first machine in day 18.

Straighten your back!



At day 18, choose "(Crack your back with relish.)" at the start of the day.

The roast
Roast the mafioso boss's butt


Break the first machine in day 19.

Justin will remember that



At day 20, do not invite Justin to the party.

He didn't die in the end!
Buy THE poster


Buy Goustling Poster from the shop.

My precious!
Purchase all the items in the shops


Self-explanatory.

Master
Win in the party game


The party game is at day 20. You can change the direction of your throw by clicking on the bottom left and/or right side of the ball.

A new life



Do not throw the rock in day 8 and 15. In day 14 and 15, say that you want to use the Time Machine to save her. Purchase the last time machine part and go to the past.

The path to happiness



In day 21, decide to go out with Mia and leave the city.

Who's Short-paws now?



Throw the rock in day 8 and 15. In day 14 and 15, say that you want to use the Time Machine to shorten all the dinosaur's paws. Purchase the last time machine part and go to the past.

Stonks!



Throw the rock in day 8 and 15. In day 14 and 15, say that you want to use the Time Machine to become the best engineer using the knowledge from the present. Purchase the last time machine part and go to the past.

Let the savior come



Throw the rock in day 8 and 15. In day 14 and 15, say that you want to use the Time Machine to prevent the extinction of T-rexes. Purchase the last time machine part and go to the past.

It is fated



In day 21, stop bidding (either after you ran out of money or until a girl gave up) and leave the auction. Chase the girl if prompted.

Backbone



Keep Mia on self-confident (->) mood, asking her to stand for herself. The final decision is made on day 16.

Soft as a feather



Keep Mia on all-forgiving (<-) mood, asking her to forgive everyone. The final decision is made on day 16.

Birds that fly low



Persuade him to quit his job in day 5.

A T-rex walks into a bar...



Persuade him to keep his job in day 5. As for his novel, which was done in day 4 and 5, I chose the following options:
- To make her watch the most cringey blind date reality shows.
- A whoopie cushion!
- Quantum Nostril.
- "I was fighting for a laugh, but the joke got out of hand."
- The hero becomes a rapper and releases an EP about his adventures which immediately becomes platinum.

Justin Bizarre Adventures



Persuade him to keep his job in day 5. As for his novel, which was done in day 4 and 5, I chose the following options:
- They need her for sinister experiments, to create a new species.
- A cannon that warps time and space and creates black holes!
- Jonathan Joestar
- "My loved ones are in my heart. This gives me strength!"
- After his victory over the aliens, your main character becomes the Master of the Universe.

Justin Lynch



Persuade him to keep his job in day 5. As for his novel, which was done in day 4 and 5, I chose the following options:
- They are forced to abduct people by yet another, even more powerful civilization.
- His family's blaster, handed from father to son, and full of secrets!
- His past is shrouded in mystery, and so is his name.
- The villain was initially engineered by the hero. So the hero goes, "I created you, but you went haywire! The time has come to shut you down!"
- After his victory, the hero flies off the handle, seduced by immense power. Little by little he starts to subjugate the Galaxy.

Puppies! :3



Keep Dysella's mood on delighted (->) state, especially on day 2 and 4. You're on the right track if you are on the right terms with her when you called her on day 12.

Rough and tough



Keep Dysella's mood on infuriated (<-) state, especially on day 2 and 4. You're on the right track if you aren't on the right terms with her when you called her on day 12.

Bon ton



Keep Bon's mood on hostile (<-) state.

Busted



Keep Bon's mood on friendly (->) state. Make sure to convince him to become a cop at day 3 and 15 and let him go to the city hall at day 19.

Lieutenant Bon



Keep Bon's mood on friendly (->) state. Make sure to convince him to become a cop at day 3 and 15 and convince him to not go to the city hall at day 19.

Still going strong



Break all of the Bloodied Leaf members' machines in day 17-19.

Well-earned rest



Do not break all of the Bloodied Leaf members' machines in day 17-19.

What you deserve



Do not break Lance's engine (his third and last request) in day 19.

Turning the leaf



Break Lance's engine (his third and last request) in day 19.

Monke primacy



Fix all of Sye's gadgets when she comes to your shop at day 8-12.

Amazing SYEnce



Destroy all of Sye's gadgets when she comes to your shop at day 8-12.

Embrace romance



Keep Sye's mood on zealous (->) state. Encourage her to approach her colleague at day 8, 9, 10, and 12.

Going solo



Keep Sye's mood on pedantic (<-) state. Do not encourage her to approach her colleague at day 8, 9, 10, and 12.

Chasing the dream



Keep Tryx's mood on agreeable (->) state. Keep on talking about her neurobiologist study. Encourage her to return to her studies at day 8. At day 11, choose "You're right. Dwelling on the past and trying to analyze it is no use. Everything will fall into its place naturally.".

I'm fine...



Keep Tryx's mood on shut off (<-) state. Do not encourage her to return to her studies at day 8. At day 11, choose "If you don't sort out your past, it will keep haunting you... until you do sort it out.".

Love is...



Keep Sid's mood on romantic (<-) state.

Johny Silverhead



Keep Sid's mood on rock! (->) state.

I bought a few friends



Keep CJ's mood on yay!!! (<-) state and don't encourage him to think about real friends in day 15 and 16.

Think about it



Keep CJ's mood on musing (->) state, encouraging him to think about real friends day 15 and 16.

No more jokes!



Choose to return the printer to the old man at day 21.

No more teasing!



Choose to keep the printer at day 21.

Ultraman for giving an additional condition in unlocking "What bros do" achievement.