Does Izuku lose One For All permanently in My Hero Academia: Heroes Rising?

No, Izuku does not lose his Quirk permanently. Although he transfers One For All to Bakugo during the climax, the transfer is ultimately incomplete because the process is interrupted. All Might later discovers that the Quirk remains inside Izuku, theorizing that the previous wielders chose to let him keep it.

Why did Nine target Katsuma Shimano?

Nine suffered from a terminal illness that worsened as a side effect of his physical modifications. To cure himself, he required a rare Cell Activation Quirk. After failing to acquire it from the children's father, Nine discovered through his gang that Katsuma possessed the exact Quirk and blood type needed to cure him.

What happens to Nine at the end of the movie?

After being heavily defeated by Izuku and Bakugo, Nine is left severely weakened and incapacitated. Before he can recover or receive help, Tomura Shigaraki tracks him down and kills him out of spite. Shigaraki then vows to fulfill their shared vision of a new society.

Do Izuku and Bakugo remember sharing One For All?

No, both Izuku and Bakugo lost the memory of wielding One For All during the final battle against Nine. When they wake up after the conflict, they have no recollection of sharing the Quirk, though they remain bonded by the experience.

Where are the professional heroes during the island attack?

The professional heroes are unable to reach the students initially because Nine and his gang deliberately destroy all means of transportation and communication on Nabu Island. This cuts Class 1-A off completely, forcing them to fend for themselves until reinforcements finally arrive after the battle concludes.