Fundamentals

Question 1

Difference of public vs private service

Answer 1

Public internet = iykyk
AWS public zone = accessible via public endpoints
AWS private zone = deployed in a vpc

Question 2

Describe communication path from an asset in private VPC to a public AWS service

Answer 2

Using an Inet gateway from your VPC goes direct from the AWS private zone to the AWS public zone, not over the internet.
Giving an EC2 instance a public IP projects the ENI into the AWS public zone, not onto the internet.