I may need to kindly ask if you're playing the full game version?
The stage progression is as follows:
1st – Tentacle-themed stages
2nd – Lava stages
3rd – Slime stages
4th – Devil plant-themed stages
Additionally, I’d like to inform you that the demo version includes stages up to the lava stages.
I apologize if this has caused any confusion. 🙏
Also, I’m really glad you're enjoying our game! 😊❤️
— Kumotori