Hey Sinem! In reference to your first question, they generally mean the same thing. We would use the past simple-"the things he did are unspeakable" in this case here. When we talk about something that happened in the past we sometimes want to refer back to something that happened before that time. We can use the past perfect. For example: "He was kind but the things he has done are unspeakable".
Follow my finger/follow my point mean completely different things. The former is a direction to observe someone's finger I assume. "Follow my point" is similar in meaning to "do you understand?".