I have sudden pain in my chest. Alone. Should I call a friend?

Call 911. If you have chest pain that scares you, call 911. If your friend is a doctor and lives next door, then you could call the friend. Otherwise, go with experts. If you wait a minute and it passes you can skip 911 and call your doctor for an appt - soon.
Depends. Depends on severity, how long it lasts, other symptoms, such as feeling lightheaded, nauseated, short of breath, in which case would call 911.