The pre-requisites can be found on the official Qlik Help Site. See Planning your Deployment for up to date information on system requirements, port listings, architecture, and other information helpful in planning a deployment.
An upgrade checklist can also be found under the reference below.
Resources to plan and execute a successful Qlik Sense Enterprise deployment or upgrade.
Environment:
System requirements:
See the Qlik Online Help System Requirements for the relevant version you are planning the upgrade to.
Up to date instructions for your relevant version:
Installation assistance video:
Step by step example and best practices:
General upgrade advice and troubleshooting help: