Answer 1

The link from Angus demonstrates how to access a *.csv file, which is a special text file, but not a native excel sheet. If you need to access certain cells or ranges for reading / writing, you should use a module that can do this. I do theese things frequently and are using xlwings, which offers also a good support. There is a basic version for free, and a pro version that will be charched.
https://www.xlwings.org/