Sure is. Deadly Class is based on a comic. The comic provides the foundation for the show's plot, characters, and world-building. However, there are always some differences when adapting from one medium to another.
To determine if it's Free Comic Book Day, you might want to look at local comic book store promotions or search online for the official schedule. Usually, it's widely publicized, but you have to stay informed.
Yes. The Deadly Class comic came to an end after a fulfilling run. It had a satisfying conclusion that tied up loose ends for the characters and the overall story arc.