These are basic English grammar questions you're asking.

Yes, exactly. A mind, to keep itself fresh, should constantly churn, revisiting new and old concepts in the same moment.

It simply means you as you refer to yourself. And your refer to yourself, when you are the subject of a sentence, as "I." Period. Not as Ryan. Just plain ol' "I."

English seems to have fewer periods (".") than it has Periods ("Period.").