Q:

Started with Ubuntu 14.04 then upgraded straight to 16.04

Looking back as a totally new user, I began with Ubuntu 14.04. After a couple of months, still being clueless as an Ubuntu user, I was presented with the option of upgrading to Ubuntu 16.04. Version 15.04, unfortunately, was niether installed by me nor was it offered as an option by my OS.
To further complicate and confuse matters, as I went through the process of help offered to me on (my 2nd askubuntu question) I learned that Grub was not installed. I installed it and it is now gone again.
At this point, since my 2nd askubuntu question. I have had more than just lag and freeze problems. Once it went from running Chrome to suddenly flipping to no apps running with everything on upper right (internet connection to start menu -- not in sight.) I rebooted and it ran smoothly for a few hours. I continue to reboot and reboot.
Question 1:) Could damage have been done by this (skip an upgrade) from 14.04 to 16.04? Kernel problems, perhaps?
Question 2:) Is not Grub an integral part of the Ubuntu package that would not normally need installing?

A:

1. Yes a damage can be caused if the upgrader started to upgrade software and you stopped it by force. To fix any issues run these commands by terminal:
sudo apt-get update
sudo apt-get install -f
sudo apt-get dist-upgrade

The 1st command updates the package lists, the 2nd command fixes any broken packages and the 3rd command upgrades all the packages and fixes inconsistencies (it doesn't upgrade the distro, don't get confused by the name)
2. Grub package is installed by default at all linux distros. When we say install grub, we don't mean the package, but we mean the command grub-install which installs the bootloader at the hard disk (usually the first partition) so that you can boot to your operating system. If grub is gone for some reason then you won't be able to boot at your operating system (you need to have a live cd in order to fix it).
If by "I learned that Grub was not installed. I installed it and it is now gone again." you mean that you don't see the grub menu when you boot your machine, then you need to hold shift as you boot to get your grub menu as @pfeiffep said in his comment.

