Answer and Question for Spoilers below

Q : Why did ML killed FL in 1TL(1st time line)?
A : ML wasn't the one who killed FL it was the look a like of him a sorcerer who Killed FL while disguised as ML.
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Q : Why does ML Glare/murderous intent at FL whenever he saw her?
A : It wasn't actually Glare, he got that yandere stare for her (Obsessive, intense love)
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Q : Why does FL think ML killed her?
A : She thought he liked Julianna (btch)and she she found out he killed her BUT that's wrong while she was dying after ML lookalike slashed her she saw real ML come and said "Thank Goodness" to him(So she knows he didn't kill her)
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Q : What did ML do after FL passed away in 1TL?
A : He hugged FL cold body for hours until sunrise, he cut FL wrist with his sword and while everyone was knocking at the door prince included when they finally managed to enter ML slit his throat with his sword and died too.
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Q : What is the sword ML carries special feature?
A : anyone whose blood is sucked by that sword the owner if the blood wish will be granted.
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Q : Why is FL memories distorted and why can't ML say he have His memory from 1TL?
A : while dying FL thought if she didn't love him or he loved her ML might have been happier which led to sword having her wish granted as she couldn't remember last of her memory when ML came to her and mistake it for him killing her rather the lookalike.While ML wish to protect her also been granted she he slit his throat but with restriction that he can't say anyone that he have his memory from 1TL.(it eventually clears out in the ending)
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Q : What happens to Julianna (villainess)?
A : She was plotting with 2st prince to kill 2nd prince, coz he wanted the throne but his father the king knew his personality isn't fit for a king. He plot came to light and she was imprisoned in dungeon but escape with the help of her Chamberlain (the sorcerer) ML knew but he didn't interfere. When Jillianna opened her eye she was chained and was R*ped by and ugly oldman while her Chamberlain watched, He can now break her and have it all to himself now.
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Q : What happened to the Ex-Finance of FL?
A : he was removed from his position as crown prince for framing FL, embezzling royal treasure for getting gift to his lover(ugh) hence his litter brother was given the position of Crown prince.he and his lover both got caught.
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Q : Does FL family mainly brother abandoned her?
A : Yes and No, they love and care for her, but the lover of ex-finance of FL r*ped him which left him no choice but to act that way towards his sister, FL hugs him but he says "he's Dirty" which FL replies with "you're not dirty".
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All in All ML And FL gets married in end and off ML is still yandere but he doesn't want to see FL get hurt his love his just intense to a max level