2.) I know there are different types of Judaism (Orthadox, Reformed, Conservative, etc). Do all of them observe the Yom Kippur customs and traditions?
Atonement is a core part of Judaism, and if you’re a practicing Jew who understands how prayer works, you tend to go to synagogue on the High Holy Days though it’s not uncommon for Jews to observe at home.
There are slight differences in the various movements (i.e. some services have more English than others).
Nothing changes the core tenet of atonement and forgiveness. We don’t believe in the concept of “original sin.”