I'll try and answer these best I can:
1. Alma and Trace's quest is a prerequisite for receiving tasks from Tey and starting the Sunrise/Sunset Beats. It's a fairly straightforward story, here's how its first few steps go to get you kicked off:
Visit Alma at the swim park -> On Trace's impregnation page: "News about your friend Alma" -> In the Witch's Library: "Inquire with Pixie about Trace's request"
After doing the above, future nudges are supplied on the rest screen which can help you through the rest if you get lost.
2. Cheat Codes I implemented into the game to input via Zen (such as infinitemana and freedrink) do not cause any interference with normal gameplay and will not stop you from doing anything.
3. Since you asked for all slimes, the things you need to do are:
- RYE - Make Reservation "Twintail Trick Set" -> Town Hall "Ask Quinoa about an orange slime employee named Milli" -> Mint's Impregnation Page "Do you know Rye's Aunt Minnow?"
- CALLIANDRA - Do the Alma Trace quest as outlined above, you will be in Calliandra's turf before you know it.
- QUINOA - Simply Heavy Impregnate her 3 times.
- LICORICE - After Hyper Impregnating her she relocates to Town Hall. Engage with the activity she gives you and eventually you'll clear her story.
4. To view new vision stuff, complete Sunrise or Sunset, then you:
- Do the hard task provided by Licorice,
- Solve a riddle from PawaMomo,
- Recheck on the Vice Characters and clear Hailey's Story, and
- After Stacy has 20 kids Mint's mom will show up in town square; Then you can visit Mint a few times and do a goof and it'll unlock some echos.
Hope that assist you and anyone else who may have hit a snag. I'll consider adding more nudges to Trace Quest in order to make it a easier to get rolling.