You can check the estimates in the graph provided in the tutorial.
Most of the tutorials are self sufficient. But you should have some knowledge of Python to understand some project based tutorials like Predicting Titanic Survivors with Machine Learning.
It depends on your need. For example if you want to use cutting edge statistical methods , R is a better options while Python is better when you want to build a scalable product. These articles will help you understand it better:
Hello Kirk, which area of research do you think needs immediate attention for advancement of machine learning/ data science?