So I just finished the demo, and since I don't understand Spanish, I'll give a review of the gameplay.
It's...honestly not good. One thing to point out is the enemy balance is wonky as balls. Some enemies are a relative match for your units, but then for some reason an enemy 2-3 levels higher of the same class has radically boosted stats. Some maps have so many powerful enemies that the only way I could get through alive was to abuse Seth. The biggest offender of this are the bosses. In Lyn's story, Eagler was so strong that I was forced to attack him with Micaiah because he one-shotted nearly all my other units. Ludgren was absolutely BS. No safe way to attack him, high attack and defense, and 60 HP. The only reason why I won was because Micaiah was able to survive 1 hit allowing me to kill him with Thani. When we get to Eliwood's story, that's when the bosses quickly get out of hand. For the first 3 chapters their fine, but then the defense chapter comes and you are faced with a boss who will double and murder all of your units besides Seth, and from then on Seth became the dedicated boss killer (besides promoted Julian) because all of my other units get annihilated by the bosses. The bosses are simply too strong for anyone else to reliably take on. It feels like you designed the bosses specifically for Seth to fight and anyone else might as well not bother.
Moving on to allied units, there is a distinct lack of unit types available at your disposal. This is exemplified majorly in Lyn Mode, where you have sword and magic units making up 90 percent of your army. The only other units you have is one Lance wielder in Florina and your two nomads. You have no axe units, which is a big problem because there are still a lot of lance wielding enemies you have to face and not enough Lancereavers to go around (Also you can still for some reason buy Axes in Lyn mode even though no one can use them), and the final two bosses would have been much more manageable to deal with if I had an axe unit to use. There are also no other cavalier units besides the promoted Seth. It doesn't get much better in Eliwood mode, where you then only have Seth and Hector to use axes. Granted Seth is all you need because of how busted he is, but I would like a little more variety. Also, the unit balance seems off. A lot of units feel too weak to reliably use when they join unless you give them a considerable amount of babying, which is how units like Ephraim, Soleil, Lyn, and Eirika saw any use because of me feeding them so many kills to not be completely useless. What makes it worse is that I'm unable to have nearly of my units grow more because of a distinct lack of promotion items. This demo has 27 chapters, and there are only 2 promotion items; one for Julian and one for a mage of your choosing (except Troubadours for some weird reason). Because of this, my main team is nearly maxed level for every unit and unable to advance any further. I know I have other units that I can level up, but by that time I already have a main team I want to use and the enemies are too tough for my other units to reliably fight. There really needs to be more promotion items. The only consistently good unit is Seth, and he borders on busted. Fantastic growths and can apparently go beyond the level 20 cap for the advance class, which might seem like a bad thing, but because of the bosses being ludicrously OP, Seth is the only reason I'm able to progress through this hack at all. Either nerf the bosses so this doesn't become the Seth show, or boost the stats of your units so they don't become dead weight. What also sucks is that a lot of your characters are lords and when one of them dies, you get a game over, so now you have about 8 units you can get a game over from, which becomes a serious issue with the last two chapters of this demo.
Now on to how the chapters play out. For the most part, it's standard FE 7 affair in how the enemies are laid out, but I really hate how reinforcements are inconsistent in how they behave. Sometimes they're normal and appear at the end of the enemy's turn, but then they sometimes act like the ambush spawns of old, and sometimes the two are thrown together on the same map. Why is it like that? Just for the sake of difficulty? Be consistent in how the enemy reinforcements appear. Then there are the few times where you add in a custom map, and these are, quite frankly, awful (except the prologue chapter). The first one to talk about is where you have to protect Levin. What makes this chapter terrible is that the enemies are insanely strong compared to your units and unlike Merlinus, Levin moves around the map and has no sense of self preservation since he always was to run right where there are enemies. Also, it seems that you made all of the gaiden chapters part of the main story, even the Hector exclusive ones. The next one is when you have to defeat the mercenary company is obnoxious because there are so man enemies and it ends with a boss who Seth could only take on. Everyone else got one rounded by the guy. Then we come to the last two chapters of the demo, which are undoubtfully the worst of the entire hack. I like the concept of having to escape the Dread Isle, but the way you went about it is just infuriating. You don't get battle preparations of any kind and you are forced to use specific units. Now if you neglected to use the units the game forces you to use on those maps, then you're shit out of luck. They will be completely useless and most likely die, and if it happens to be a lord, game over. This first map can actually be unwinnable if you failed to properly train your units. The next map isn't any better where you have to get your footlocked Eliwood on to the other side of the map to talk to an NPC while being swarmed by enemies. Also, if you happened to de-equip the units you're not using and then get to these maps, they will be extra useless. Honestly, I think you should allow for Battle Preparations for these two chapters because new players will be caught completely off guard and will reset multiple times just to get through these chapters.
Also, what's up with some of these portraits? Some look off like Eliwood and Sora (he looks like someone cosplaying as Soren) and then there's Jaffar. What the hell happened to him?
Now for some positives: I liked that you added in two range swords to allow sword units more options, though I wish there was a physical variant. Having them be all magical weapons when these units have low magic growth seems like a waste. Some of the new battle sprites look good, like Soleil, but then some look choppy, like Seliph and Leif. The addition of Short Bows allows more options for Bow users. I like the personal touch of giving the Lords each unique weapons, makes them feel more individual. And I like the new music you added to the game, though I question why the Ace Attorney music sounds off when Ace Attorney initially released for the Gameboy Advance.
All in all, this hack needs a lot of work. I see potential for something great, but right now it's too frustrating between OP bosses, weak allied units, bizarre enemy balance, and inconsistent enemy behavior for people to really enjoy it.