I HIGHLY recommend playing the game and play as you like to properly experience the story before reading this guide. This guide is all spoilers HOWEVER if you want to get ahead, you can make note of your song choices (probably easiest by colour) to help in the long run for Maestro.

You can press 'N' to skip scenes but you cannot skip songs. The song runtime is a little over an hour so depending on how much your skip, each run will take minimum 1.5 hours.

A minimum of 3 full playthroughs is required. To avoid a full 4th playthrough:
1. Romance Freddie and Persphone on the same run, stay with Persphone and flirt with them both
2. Save Freddie and choose her, complete the game with her
3. Reload starting at It's Time, and let Freddie go, then finish romancing Persphone
4. Reload one more time at Confront Persphone, and break it off with Persphone to get the solo epilogue

You will need to do a final load of The Throne since there is 4 options for it plus probably many others for the Maestro achievement (7 variations of the Ritual alone!), but you don't need to complete the run for it to count!

Adrift - choose trait and continue to use it often* in songs throughout the playthrough

• Charming (Green) - Achievement - Charismatic
  
• Kick-Ass (Red) - Achievement - Fiery
  
• Clever (Blue) - Achievement - Cunning

*just the majority, can pick other options. Achievements pop at the end of the game

Achievement - Heartbreaker

• Flirt with every suitor (Freddie, Pan, Apollo and Persphone)*
  
• You are still able to just choose 1 suitor afterward
  
• Possible by the end of Act 1 if you choose Persphone after Old Wounds, otherwise you can still get it in Act 3
  *not required in one save file

The Chorus is in Accord

I Can Teach You

• Choose Freddie (Green) Achievement - Not a Lost Girl
  
• Choose Yourself (Red) Achievement - My Time to Shine
  
• Choose Pan (Blue) Achievement - The Choice is Yours

Phantom Pains (Calliope's House)

Challenge a Queen (The Underworld)

Old Wounds (The Underworld)

• Choose Persphone - Achievement - Queen Without a Throne
  
• Choose Apollo - Achievement - God of the Sun

Achievement - Finish Act 1 - The Deep End

Cast a Spell (The Reliquary)

• Hecate and Asterion in love! (Red/Green) - Achievement - Meant to Be
  
• Let Hecate talk (Blue) Achievement - Arrow of Eros Undone

Let's Have This Dance (Pan's Tree)

• You will visit Pan after the Reliquary. Ask questions and flirt

The Ritual (Aphrodite's Party)

• Save Aphrodite (Red) Achievement - All the Help You Need
  
• Allow Aphrodite to Die (Green/Blue) Achievement - Lost in a Song

You and I (The Underworld)

• Stay with Persephone after Old Wounds* then visit Persephone after the Ritual + flirting

Here for the Ride (Apollo's House)

• Go with Apollo after Old Wounds* then visit Apollo after the Ritual + Flirting

*not actually sure if the Old Wounds choice affects the romances, but when I stayed with Persephone I flirted and wasn't given the choice for Apollo's heart after.

Look Into Me (Medusa's Lair)

• Defeat Medusa (Red/Green) Achievement - Like Heroes Before You
  
• Help Medusa (Blue) Achievement - Snake Charmer*

*MUST have Clever trait

Achievement - Not Taking Any Chances

• When in Athena's office tell her that Medusa tried to eat you

Achievement - Finish Act 2 - Across the Styx

The Throne (Real Underworld)

• Take the Throne (Red) - Achievement - This Hell Is Mine*
  
• Destroyed the Throne (Red) - Achievement - Abdication
  
• Leave Orpheus on the Throne (Blue) - Achievement - The King of Hell
  
• Give Persephone the Throne (Green) - Achievement - The Queen of the Dead

*MUST have the Kick-Ass trait

It's Time (Real Underworld)

• Save Freddie (Red) - Achievement - The Ultimate Sacrifice
  
• Let Freddie Go (Green) - Achievement - Saying Goodbye

If Only (Apartment)

• If you save Freddie + flirting

Adrift Reprise (Auditorium) - versions vary depending on if your saved Freddie or not - both needed for Virtuoso and Maestro

• If you saved Freddie, it's a solo
  
• Sacrifice Freddie, you have other muses singing with you

The Trial (Olympus)

• Punch Athena (Red) - Achievement - Talk to the Hand
  
• Forgive Athena (Green) - Achievement - The High Road
  
• Tell Athena she's out (Blue) - Achievement - Brand New Chorus

Achievement - Finish Act 3 - The Muse's Encore

Romantic Reprises
Note: There is always a moment when you make a clear choice to pursue the romance. This usually starts with or is during the first romance song, with the exception of Persephone.

• If Only - Freddie - Achievement - Brave on Time
  
• Here for the Ride - Apollo - Achievement - The Answer is You
  
• Let's Have this Dance - Pan - Achievement - Share this Dance
  
• You and I - Persephone - Achievement - Together, Victorious

Everything

• If you romanced no one - Achievement - Everything has Changed

Achievement - Finish the Game - Against All Odds

Achievement - Virtuoso - Listen to all songs

• All songs listed above but you also need to listen to both versions of Adrift (Reprise)

Achievement - Maestro - Listen to ALL variations of songs

• There's a guide here that has been listing them so rather than repeating check there

https://cs2bus.com/sharedfiles/filedetails/?id=3019778120

You need at least 3 playthroughs of the DLC. Took me about an hour and 15 minutes to beat. Replays took about 30 minutes (skipping old scenes).

One More Song
Triggers after the first song if Orpheus isn't on the throne.

Return of the King
Start with a base game save with Orpheus on the throne and it will pop after the first song reprise(?) when you're in the modern world (Thanks fluffycatsandtattoos on Reddit <3)

Outside Looking In
During speed dating, choose cat ears, woman yearning for love, a date with marvellous hair (might be out of order), and smartly dressed man. After that, choose a negative dialogue option (red or blue I think) to end the song. Then tell Hermes "maybe it's not meant to be" and it should ditch Hermes. You'll meet Medusa in the bar. You'll get the achievement after her song.

You can also get Medusa I think by finishing the full song and choosing a negative option with Hermes but I don't have a guaranteed direction like the above.

The Meaning of Love
After speed dating, choose "I'll have to keep trying" or other positive options to stay with Hermes and you'll meet Eros in the bar. You'll get the achievement after his song.

Orpheus Has No Rizz
Flirt with Medusa/Eros, Hermes and Grace (and fail hah)

Ending Achievements
You make the choice during Something New but the achievements pop after the epilogue song based on your choice

A Mortal Life
Ending as a mortal (red choice)

In Search of Fate
Ending with a quest (blue choice)

Back to the Dead
Ending with "no this is over" (green choice)