QIf I play Nature's Guidance as my third or fifth card this turn and use it to return this follower to my hand, does this follower's ability trigger?

AYes. It was on the field when you played Nature's Guidance, so its ability triggers.

QIf I play this follower as my third card this turn, does it trigger its own ability?

ANo, it doesn't. It wasn't on the field when you played it, so its ability doesn't trigger.

QI begin my turn by playing this follower and a Chipper Skipper. If I then evolve the Chipper Skipper, does this follower's ability trigger?

ANo, it doesn't. Evolving followers doesn't count as playing a card.

QIf I play this follower as my fourth card this turn, and then play a Fairy, can I draw a card with this follower's ability?

AYes, you do.

QIf I play this follower as my third or later card this turn, and then play two more cards, can I give my leader +1 defense with this follower's ability?

ANo, the cards you played before this follower count too. Since this follower wasn't on the field when you played your third card this turn, you can no longer give your leader +1 defense with this follower's ability this turn.