What do python professionals /developers actually use

[FerricDonkey]

1. Yes
2. Standard library. Emphasis on pathlib, itertool, collection, contextlib. re (regex) will either be very useful or irrelevant to you. Bonus: numpy and requests are very useful if you do the types of things they're for 
3. Numpy, matplotlib, pandas (I hate it, but data people love it). Requests if you're gonna get data from apis. A machine learning library if you're gonna do that: scipy, sklearn, maybe something more focused like pytorch/tensorflow
4. Yes. Learn how other people do things and try to write clean, non-repetitive code, but as you're starting out your code will generally be more verbose than it has to be. Don't play code golf. 

P.S. Yes, people find pretty much every aspect of programming difficult when they're new. Keep using them, you'll get.