So, I'm sorry to say that I'll need another weekend for the next demo due to time/energy spend on two new Gamemaker Studio bugs:
1. the WITH(..) functions sometimes does not detect all instances in the room. I've recoded the most critical usages of the function but given that I use WITH(..) in 1600+ places in the project, that's just painfull.
2. When I save the project under a new title (like "public demo") some external files are not recognized in the new project. Even though they show up in the workspace and windows explorer, and can be opened from both locations. And (for as far as I was able to detect) this only occurs for some of the latest files.
...
And then I discovered I was not allowed to run with the runtime version I used before.
...
GameMaker updates breaking more then they solve again really bummed me out this weekend man.
Progress report:0.21.77 (30 augustus 2019)
* The GML WITH(..) function is bugged. Switched back to the older INSTANCE_NUMBER(..) and INSTANCE_FIND(..) alternative where the results where definitely off.
* Fixed issues with swimming below the overworld bridges
* Tweaked ocotrok AI to only shoot out rocks while the character is not too far away
* Improved collision detection between wall crashing and breakable walls
* Tweaked dark world containers
* Finished overworld masking
* Finished all overworld diggrids
* Checked / edited all room hud texts
* Improved collisions when jumping into water
* Tweaked overworld tiling here and there
* Fixed sounds when jumping off a ledge into deep water
0.21.78 (31 augustus 2019)
* Lost another half day due to Gamemaker not recognizing (some) external files if you save the as a new version. :(
* Finished little devil summoning scene
* Fixed visual issue with enemy depth object
* Add 1/4th magic upgrade item to the gauntlet
* Added functional altars in front of mansion to place rings on
* Started mansion entrance scene
0.21.79 (1 september 2019)
* Made good progress on the mansion entrance sceneStuff left before releasing an untested demo:*I'll likely release an untested version when all the non-optional stuff is done and then the real demo when everything is done and testing.[IN PROGRESS]- Fully mask both overworlds- Add diggrids to both overworlds[IN PROGRESS] - Add scene to enter the mansion dungeon
- Add scene to enter the final dark world dungeon
[IN PROGRESS] - Connect the mansion dungeon to the overworld
[ALMOST DONE] - Add the magic granting devil- Tile/mask/finish fairy cave
- Check all area's introduction texts- Check and edit all enemy placements
[OPTIONAL]- Add Link's starting house
[OPTIONAL]- Add NPC's to lightworld town outside area
[OPTIONAL]- Tile/mask/finish fortuneteller house. (= heart piece hint system)
[OPTIONAL]- Fully complete overworld tilesets (=death mountain lightning+custom tiles)
[OPTIONAL]- Finish new enemies: chickens
[OPTIONAL]- Tweak masking for run wall collisions with breakable walls- Think up some sollution for the latest GML bugs I found 
[NEW] Handle GM:Studio2 issue with unrecognized external collision files
EDIT: Correction on last weeks update
:
I am informed by YoYo Games that the main bug I found in their recent updates, is in fact not a bug but only a small new feature that nobody will be bothered by.
