Answer 1

If using free version, lives replenish daily at midnight local time.

If you are having trouble with a particular concept or operator, swipe backwards to previous slides and look at comments. Often your fellow users will post clarifications, examples, or outside links.

If you are still confused or want to learn more, open a browser tab and do a web search for the topic. Stackoverflow, Quora, or blog entries on some tutorial site are all good links to check.

You can also go back to previous slide with a Code Playground, erase what is there, and write your own test code to play around with an operator or such.
Such practice is good way to make sure the code actually behaves the way you think it does.