Okay, I'm assuming English is not your first language. With that said, I'm going to quote your questions below, reworded as how I understand them, then give my answers. This way, you can at least see the way I read your question.
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Question 1: "1.- Why has the MC not yet promoted to Samantha and Shadow? Of all the girls, only they have not yet promoted; At least that the fairy form is the ascended form of Shadow and maybe later, let's see Samantha's ascended form."
My interpretation of that question: "Why has the MC not yet ascended Samantha and Shade? Of all the girls, only they have not yet ascended."
Part of what you are saying here is not accurate. First of all, Fade (as a fairy) was cursed to live in that form initially. MC released her from that, revealing her true form. Shade was never cursed and doesn't need to ascend. She is already a product of the 'shade' (her namesake) just like Fade is already a product of the 'fade' (her namesake). On a similar note, Samantha was already a succubus demon. But her power was taken away by MC early in chapter 1. He gave it back to her in chapter 2, episode 4.
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Question 2: "2.- Could it be that there will be some more history after defeating Anastasia, or after defeating it, the game will end?"
My interpretation of that question: "Will there be more history revealed once Anastasia is defeated? Will the game end after that?"
I am not sure what you're looking for (historically) outside of maybe other things MC might learn from Fereldan. But yes, the game will end after her defeat, but it will take a few episodes to end it (it won't just END abruptly right there). It will probably have a couple of branches where you can choose how to end it.
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Question 3: "3.- Do the girls who already had power, after their ascent do they receive another or change power? I ask, because some girls like the Morgana demon, before his rise, his power was to block barriers or something. When ascending became the demon of the storm, which implies that it acquired another power or change of power."
My interpretation of that question: "After ascending, do some of the girls 'ascend' again and some not?"
I think you are forgetting that Morgan was written into Serenity by MC's mother. Morganna is the 'real life' person she was created to look like. MC's mom wrote her into Serenity as a demon because she was angry with her... a problem she later regretted and apologized to her for. Morgan was always a demon, just like the others you mentioned. But to answer your question, yes, some girls ascend only once, while others ascended, then unlock a bit more power later - like Rin. Using her anger, she unlocked her full dragon form. Morgan was able to unlock more power (ascend) due to her desire to do good - not be a 'bad demon'. So she became a Tempest.
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Question 4: "4.- If they change power or acquire another: What are the powers of some girls after ascending? I say it, because some are confusing, for example: the dragon girl (I think it's called Rin), after he ascended, sometimes he shows a power, but sometimes another shows."
I'm not going to try to rewrite this one. But I'll answer with what I think you want to know...
First of all, there are six girls in MC's harem: Kat, Jasmine, Lena, Rin, Morgan, and Trixy. All of the other girls are purely external love interests or play a smaller part in the main plot - except for Lili (Valkyrie). Although not technically part of the main harem, she has a major role in the plot. Below are the main harem and what their powers are:
Kat - Seraphim Angel - Powers: Light of Judgement, All seeing (can see anyone, almost anywhere)
Jasmine - Flame Goddess - Powers: Everything FIRE. If she wills it, it burns.
Lena - Angel of Pleasure (Dark Lena - Angel of Pain) - Powers: Lena can bring pleasure and healing to any living thing with nerves in the body. Alternatively, in her "Dark Lena" form, she can bring pain to those same nerves.
Rin - Cat Dragon / Fury Dragon - Powers: Rin is the tank. Unbreakable, extreme strength and speed. In Fury form, she is larger and everything is amplified. She can only hold that form for a limited time.
Morgan - Tempest Demon - Powers: Elemental, climate controlling (thunder, lightning, water, earth magic, etc)
Trixy - Angel of Time - Powers: the only power of Trixy's revealed so far is her super speed. But she has another really interesting power that hasn't been revealed yet (and I really don't want to spoil that here).
For what its worth: Serenity will have 2 chapters total. Chapter 1 is completed. I am finishing Chapter 2. Chapter 2 is made up of episodes (my latest update added episode 4). I am guessing it should end up with around 9 episodes total, possibly 10 before the ending of the series.
Chapter 1 was is a chaotic mess, both in the writing and in the way I organized that story. It is possible that someday I will redo that one with episodes, better writing, and better organization... and it would be just a bit longer than it is currently.