Can't believe I'm saying this but, that's pretty good. You've come a long way from last year.
Here's some things to improve on:
The backgrounds are a mish mash of different games. I know most people don't do their own backgrounds since it takes work, but it really does stunt the coolness.
Selective highlighting fiasco with the backgrounds; What is selective lighting? Highlighting things to bring the player's attention and infer interactivity types. Example: the floor is highlighted brighter than things you can't stand on. This gives the player a natural visual indicator of "you can land on this". The tops of the gravestones/coffins/whatever in the background that you can stand on, are not highlighted and dont look like you can stand on them. While there is sloped ground you CAN'T stand on in the background, that has the SAME highlight as the dirt background you CAN stand on. Keeping this consistent is the key for fluid and intuitive level design. If you don't fix it, the player will pause to think "can I actually land here or not? Should I risk it?" at times which breaks the flow and confuses the player where he/she should not be confused.
Other than that the mixed sprite styles, but given that Adventure ReBirth reused GBA sprites I can let it go since you're using Chris.
Things I'd like to see:
Dropping off of, and landing onto stairs. CV4 style.
And hard mode you don't get the upgrade at all.
NO. Removing functionality like that only serves to drag things out and create a more tedious experience.
If you want good difficulty, reduce lags between actions of the AI, speed up some enemies, etc. But never remove a basic function like that completely.
I'm personally in favor of keeping the fire balls until you get hit once.