Compare Updates to Windows Build releases (like Windows 10 Version 20H2 versus 1909). They usually contain major overhauls, e.g. deprecating the Flash client in favor of HTML5, functionality enhancements, introduction to new features, etc.
Patches are normally the ones that are put out for bug fixes, security vulnerability remediation, etc., just like regular Windows Updates.
Your vCenter will always need to be higher than or equal to your hosts. Example - You cannot manage vSphere 7.0 hosts with vCenter 6.7. You would need to upgrade you vCenter to 7.0 first, then your hosts.
I would recommended to always rely on VMware's Hardware Compatibility List to see what version of vSphere your hardware can be supported on, and their Interoperability Matrices to see what versions of their product work together. Links below:
VMware - HCL
VMware Product Interoperability Matrices
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