QIf I have 2 copies of this follower on my field and another follower is put onto my field, will each copy's ability trigger?

AYes. Both abilities will trigger.

QIf I evolve another one of my followers, does this follower gain +1/+1?

ANo. Evolving does not count as putting a follower onto the field.

QIf my field has reached its card limit and I play an ability that puts a follower on my field, does this follower still gain +1/+1?

ANo. If your field is full when you play an ability that puts a follower or amulet onto your field, that follower or amulet does not actually get put onto the field.