Listing the recommended order of Upgrade for various components of Nutanix Cluster :

1. Start with Prism Central(PC) - (If Deployed)

Upgrade NCC 

Upgrade PC

Run NCC health checks. Check for impacted clusters.

2. Then Upgrade Prism Element (PE):

Upgrade NCC on all your clusters

Run NCC health checks

Correct any issues found before moving forward.

3. Upgrade Foundation to the latest on each PE.

4. Update Lifecycle Manager (LCM)

Perform LCM inventory (Which updates the LCM framework to the latest software)

During this time, Do not upgrade anything else on that cluster.

This step only updates the LCM framework itself and also performs inventory. No reboots or upgrades to the server are performed. 

5. Upgrade AOS on each PE cluster.

6. Update Firmware versions using LCM

This step should be performed only if all the previous steps are complete and health checked. 

7. Upgrade Hypervisor. 

For AHV Clusters :

Upgrade AHV to bundled version from the PE web console.

For ESXi Clusters :

For all 1-click Upgrade, we require the customer to have DRS Functionality.

1. From Vendor, Download the available hypervisor version.

2. From Nutanix Support portal, download the metadata file(JSON), if available

Note : 

For Esxi Patch Updates :

Download patch bundle and MD5 checksum from VMware to Upgrade

For more information : 

Acropolis-Upgrade-Guide

Nutanix Cluster Upgrade and What It means to you.