Windows 2012R2 upgrade

imo option 2 is the best from a ease and safety point of you. Option 1 offers can be rolled back with a snapshot. Option 3 is not simple

However depending on the amount of instances my favoured approach would be to invest some effort in creating Infrastructure As Code templates (Cloudformation or Terraform) to create both the instance and install the necessary software within the bootstrap (Or create AMI using EC2 Image Builder). This effort can simplify future OS upgrades and helps you enable automated deployments for software updates or take advantage of technologies like autoscaling

Thank you for your reply Peter.

I have one more question regarding option number 1 - In-place upgrade. What is the issue related to licensing and billing of such a machine, which was originally Windows Server 2012 and upgraded via snaphot owned by AWS to version 2019? Do I need to perform any additional steps? Will licensing and billing for a machine with the new system set up in AWS automatically?

I ask because, during installation, I can choose between Windows Server Standard and Datacenter. Will this choice change the cost of ownership of the machine and, more importantly, will such a change be automatically noted in billing?

In general, what is the licensing and billing during such an upgrade if the original machine is based on an AWS license rather than BYOL?

Kind regards