The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.
Well, obviously Deku in two forms - the younger and the older version are the main characters. The younger Deku is the one who is still growing and learning, while the older Deku has more experience.
As of now, Deku is very much alive in the manga. The plot hasn't reached a point where he meets such a fate. Usually, main characters like Deku have significant story arcs and aren't easily killed off.
He might cry a lot. Deku is very emotional, and being cheated on would be a very painful experience for him. He could also get angry, which is rare for him, but this situation would be so unjust that he might not be able to hold it in. He'd probably start to question his self - worth too, thinking that there was something wrong with him that made his partner cheat.
Another plot might involve the older Deku being from an alternate timeline. He shows the younger Deku different ways he could have developed his skills and relationships, which makes the younger Deku reevaluate his own path as a hero.
The members of the mask referred to an assassin organization made up of mutants in the novel " Perfect World." The leader was an old friend of the Willow Deity. He was suspected to be a creature from the Immortal Ancient Era. For unknown reasons, he had founded the mask organization in a foreign land. The members of the Mask Organization all wore bronze masks and obtained battle merits by hunting young heroes from foreign lands. Battle merits could be exchanged for various rewards, the most precious of which was the right to enter the Immortal Ancient Ruins.
The members of the Mask Organization were powerful. There were Venerables, True Immortals, Immortal Kings, and other experts. Their movements were strange and their methods were cruel, making the creatures of the foreign world tremble in fear. In the novel, Shi Hao had many conflicts with the Mask Organization, and he had killed many members of the organization in many battles. In the end, Shi Hao engaged in a life-and-death battle with the leader of the Mask Organization in the foreign land's Immortal Ancient Battlefield, killing him.
While waiting for the TV series, you can also click on the link below to read the original work of " Little Fox Demon Matchmaker " to understand the plot in advance!
Deku might be initially shocked. He's used to Bakugou's aggression, but an actual injury is different. He could be in pain and disbelief at first. Then, he might try to downplay it, especially if he doesn't want to cause trouble for Bakugou, because Deku is generally a very forgiving character.
In the manga, Deku experiences various ups and downs. He not only becomes stronger physically but also matures emotionally as he takes on greater responsibilities. There are also many unexpected plot twists that shape his journey.