They will be changed when the full game is released. For now, they just remain closed and don't do anything.
Viewing post in what are these secret demo doors in each world?
oh,also i had an idea for a hub puzzle,its about entering levels and exiting them to go to the same place but your stone keys reset,heres what im thinking (edit:you have 12 stone keys) :
| [other stuff above] | wall | ||||
| wall | wall | wall | wall | wall | |
| 9 stone (2x2) | 2 stone (1x2) | level | |||
| wall | wall | wall | 9 stone (1x5) | wall | wall |
| wall | [starting area below] | wall |