So, let's start with what I (single-handedly) did.:

MUSIC

-I will continue uploading new tracks, which will playing in demo

approximately ~75% of tracks done

-New tracks tomorrow!

MECHANICS

-Intro

-Main menu

-Save/Load the game

-Character movement (yes)

-transition between rooms (yes, seriously)

-Transition from one character to another

-Pause

-Fully functional inventory (pick up, use, delete, examine) (for both characters)

-Dialogues with NPCs

-Enemy encounter system and combat system (including bullet hell and heart modes)

-Dialogues in battle

-Some puzzles in ruins

-Kill counter

SPRITES

-overworld sprites of humans

-SPRITES OF ME (LAZY BEAR)!!!

-overworld sprites of the main characters (Laxo, Chank, Fary, etc.)

-sprites of minor NPCs

-battle sprites of enemies in Sewers (Camilioid, Aduaduch) (you can suggest 1 more) and sprites of their bullets (bullets are already working)

-Overworld sprites of some characters who will not appear in the demo but will be in the game later

-Sprites of items

-Intro animation

-Hearts and their additions (frying pan-shield, etc.)

-The Sewer TileSet is partially ready, the Ruins TileSet has not been changed(yet)

And now for what else needs to be added to the game before releasing the demo:

-Maybe remade Humans's sprites (RON'S PORTRAIT!)

-Make Bosses's battle sprites (I have small skill of doing this, because it mustn't be bad)

-Make Bosses's attacks (it's easy for me)

-More enemies and sprites of them (Suggest your please)

-Remade attacking system

-Design new Toriel's overworld sprites (she will appear a little)

-Make ARMOURs and WEAPONs system (easy for me too)

-Make puzzles in Sewers

-Maybe add new animations/sprites for characters

-Finish Sewers TileSet

WOW, YOU READ IT ALL! Thank you! These hearts is for you!