What's the difference between an upgrade and an update in SAP maintenance, and what tool does both?

What determines whether an add-on component can be uninstalled?

What account does SUM run as, compared to SWPM, and which version applies to S/4HANA?

What do most add-ons require, and how is it generated?

Why must you update Transaction SPAM before an update, and what's it always combined with?

What is the maintenance planner, and what critical file does it generate for SUM?

What's the only precondition for using the maintenance planner with a system not registered in SAP Solution Manager?