(In easiest order to obtain)

Back to the past
You get this when you enter the main menu.

Make it personal!
Like it says, apply a setting. Turn it fullscreen.

Under The Sea
Wait 1-2 minutes in the main menu until the screensaver kicks in.

New Wallpaper!
Click on "SunsetOS" in the top right corner to change wallpapers. I bet thats the only one you had trouble with.

What's this?
Collect a Tape, they are near walls most of the time and spin.

A Taste Of Your Own Medicine!
Buy a soda at a machine (on walls) and throw it at a mugger (red NPCs)

Better luck next time...
When starting a level, get to a mugger and just stand there until he stole all your money. It's faster if you play the hardest difficulty.

WINNER!
Buy everything thats on your shopping list and leave the mall.

Avid Socialite
Just walk through the mall and spam E to talk to the shoppers.

Unlucky
The easiest way is to obtain a large sum of cash (through ATMs for example) and then round up some muggers around you and then stand there while they rob you continously.

Quack Attack!
Click 1000 times on the yellow duck on the bottom right corner in the main menu. You could either be old school and manually spam the mouse button or be Gen Alpha and use an auto clicker while you doomscroll TikTok and YT Shorts at the same time. The choice is yours G.

Personal note:
I really really like this game. It's short and not really a game but more like an aesthetic museum. The soundtrack is exactly what im failing at finding most of the time so it's much appreciated! The trading cards are also a nice feature with lot of cool facts to read. And the screensaver unlocked some key memory of mine. Just A E S T H E T I C!