2 questions. Can I change the name of my drive when upgrading from Mojave? Where does one find a copy of Catalina?

Hey everyone.

So, I might have done a stupid thing when doing a fresh install and system rebuild a couple of years ago. Rather than name my drive "Macintosh HD", I formatted it as "Mojave" before I installed Mojave. I now want to do a simple upgrade to Catalina, and would love it if my drive was simply called "Macintosh HD" since I won't be on Mojave anymore. Would this mess up anything when it comes to software finding files, loading etc? Do I have to leave it called Mojave?

Also, where does one find a copy of Catalina to use to upgrade? I want to be sure I'm using one that is problem free and rule that out immediately if things go odd.

Thanks all!