I was searching for the free version of VMware player and couldn't find it immediately. It seems like VMware has re-branded it to VMware Workstation Player and there is a free version of this for "Personal Use". If you head to this page http://www.vmware.com/products/player/ and scroll down to almost the bottom you will see a section titled VMware Workstation 12 Player Free for Personal Use. Under that section you will see a link for download. I haven't tried it yet so I don't know if there are any feature limitations attached to it.
There is an option in VMware where after you have performed an major upgrade of ESXi you can roll back to your previous version. The benefit of this is that you would not need to reinstall your ESXi and its configuration if you had issues with the new software. I had to do this on one occassion in my lab where I upgraded from 6.5 to 6.7 and my VMs would not run because the CPU was not supported in 6.7. Please remember if you are using ISO method to upgrade ESXi please ensure you select "Upgrade ESXi, preserve VMFS datastore". Selecting "Install ESXi, preserve VMFS datastore" does not mean preserving datastore means retaining ESXi as it will still do a clean install of ESXi. This method does not work for vSphere 7.0 as there are changes to the partitions on the boot device. Below are the steps to roll back to a previous version which is quite straight forward. As always perform an backup of your host configuration before you upgrade or rollback ( KB2042141 ). I have