Bob Cratchit in 'A Christmas Carol' is a symbol of kindness and perseverance. He works for the cold-hearted Scrooge and has a large family to support. Despite his difficult circumstances, he keeps his spirits up and shows love and care for his loved ones.
I'm not sure if there is a widely known 'Nurse Cratchit' as a true story. There could be someone named Nurse Cratchit in a very specific local context or a personal account that I'm not familiar with.
Yes. There is the original written version by Charles Dickens which has a very specific language and narrative style. Then there are film adaptations which often have to make changes for the visual medium. Some might cut certain parts, add new scenes for drama, or change the pacing, making them different versions in their own right.