Help me to answer three discussion questions in Mechanical Engineering(Design for manufacturability) class

First question:

Why is it still common to see manufacturers select injection molding compared to additive manufacturing? Elaborate and support your arguments. 

Second Question:

What is the purpose of the parallel plate, edge finder, and coolant, respectively?

Third Question:

What are lead-in, lead-out, ramp, plunge, and cutting feed rates, respectively? Use your own words, and briefly state the definition of each term. Discuss the differences and similarities among these parameters. What is the relative magnitude (of the four) that you would suggest using based on the characteristics of these parameters? Justify your suggested relations.

Please help me to answer all of those questions in detail.