I’d now like to attempt the first hypothetical, going back in time 100 years into the past.
The world is still dealing with the aftermath of World War 1. Over 16 million people died from that conflict and 50 to 100 million died from the 1918 influenza pandemic.
Question: Would a 2019 Flu shot, before I stepped into the time machine, protect me against the 1918 Influenza? Or would a hundred years of mutation make it worthless?
Assuming that I was protected from the virus, the best job to get for someone without any 1919 era skills would be as a grave digger. The deaths from influenza were so overwhelming back then that mass graves were common. Working in a hospital might be another viable job since it would be hard to fill.
Staying out of the cities would be a good idea. The “urban penalty” due too poor sanitation and water systems was still a challenge and wouldn’t be fully corrected for another twenty years:
In 1900, waterborne diseases accounted for nearly one quarter of reported infectious disease deaths in major cities. In the next few decades, waterborne disease mortality fell dramatically. (Harvard University)
I would have ten years until the Great Depression of 1929, which means I could use my knowledge to invest in the stock market and get out before the crash.
Reading would be more of a habit as would be going to public performances and interacting more face to face with neighbors and the community.
It wouldn’t be an easy life, but I think most people could adapt if they had to.