I just tried you game.
I have to say that I was positively surprised. You have learnt a lot, this game shows big improvement over some of your previous games!
I understand that the demo is just a pre-alpha, and thus a lot things are yet to be done and bugs fixed.
One bug I found was that it's possible to select all four characters for a single match. That obviously creates multiple other bugs with the winning ceremony etc.

Also, I think the controlling is a little weird as you can't move to any other direction before you've released other buttons.
I mean, if you're pressing left, you can't start moving up before letting go of the left arrow and then pressing up again, so you have to even release the up key and press it again in order to make the character move up.
(That was one very bad explanation, but I hope it gets the point across..)
One thing you should consider is to balance the different attacks so that quicker attacks deal less damage and slower attack more damage.
Because currently there's simply no sense in doing anything else but holding down the button for the fastest attack, and the slower ones only dealing the same +1 damage are useless.
Balancing the damages is really essential so that every attack has their pros and cons, like this:
Attack 1
- Fast (that's a pro)
- Deals only little damage (that's a con)
Attack 2
- Slow (that's a con)
- Deals much damage (that's a pro)
If any attack has only cons it will never be used, and if an attack has only pros it renders all other attacks useless.
So, balancing, balancing...

Also, the current health system is just weird. Why call it HP if the more you have means the closer you are to dying?
Either make it so that every player starts with 70 and then it decreases, or call it damage instead of HP. 70 also seems a bit weird value to choose, normally games operate on percents, so things like HP are based on values 0-100 (1 HP = 1%) or 0-10 (where every 1 HP can be considered as 10%).
Then just a minor thing, but it's kinda funny how the loading text animates backwards, I mean, the three dots disappear instead of appearing one by one

I hope you consider my feedback valuable. I know this was a pre-alpha, so this should not be considered as the actual product. And because I knew that, I assumed it would be good to tell you what things may need more work and how you could make this game better for the actual release.
Good job so far, keep working and improving the game!
Also, one more question/suggestion.
Are you going to add enemy AI so that one can play against computer instead of another human player?