UX vs UI

Answer  the following two questions in a straight forward way (question-answer). no need to add introduction just go direct to the answer.

Question 1: According to the attached resources and your own experience: what is the difference between User Experience (UX) and User Interface (UI). And what is the link wit Design Thinking?  Please use the attached document as a source to answer this question. Apart from that, there should be personal thoughts.

Question 2: Take a look at this video from Quirky about cardboard prototyping. Do you think it’s a low-fidelity prototype? Why?
https://www.youtube.com/watch?v=k_9Q-KDSb9o

1 page for each question-answer.