1. Generally don't overwrite things, make a copy and edit it instead.
2. There are a lot of things you can change from within the program that you could make a backup off, such as Symbol Catalogs (.fsc files, live in the @Symbols directory), Drawing Tools (.dto files, lives in @System\drawtools), templates (*fct, @Templates), symbol catalog settings (.sis, @System\Symbol Catalog Settings), Symbol Catalog Master Filters (.sif, @System\Symbol Catalog Master Filters)
3. No. There isn't a way to reset other than reinstall or restore from backup.

Note that the files you are most likely to change (accidentally) are drawing tools. Symbol Catalogs can only be changed by loading the symbol catalog as a drawing (instead of into the symbol catalog window) something most people don't do and pretty much guaranteed wil never happen accidentally. Same with templates, you need to load these as a drawing to change them, changes in a drawing never change the template it is based on. Symbol catalog Settings are also somewhat easy to accidentally modify, if you click advanced in the select symbol catalog window.

Things that only affect the current drawing are changes to fill styles via the Fill style dialog, as well as editing symbols via the symbol manager. The latter only edits the copy of the symbol in the drawing, and not the global symbol catalog.

Well, things are not that much different. Yes, the miniatures and grid have been switched out by a VTT, and handwritten notes are now done digitally, but we still sit around the table, argue about the rules, and consume tons of snacks. And with a VTT you don't have to have the minis for everything. And it saves lots of space on the table.

I used to be the DM that described the place and had them draw their own maps, but I realized that it took away a lot of the game. Players would spend unnecessary much time drawing, and they would frequently ask me to repeat distances (which I could hardly refuse to do, the characters were there in the middle of the dungeon and could re-check things as often as they liked).

This is why I love the VTT and projector approach. My players only see what their characters see in that moment. It saves me from describing every minute details about direction and distance, but the players see the current situation. I don't let them see back to where they have been, only the exact place they see right now. If they want a map, they can draw it, but I save a lot in explanation, and it looks so much prettier. And I can put in semi-surprises as part of the map drawing. Now, they need to actually use their eyes to spot certain things instead of me describing everything.

Most of the commands are available in the help file, although admittedly, it hasn't ben updated with the newest commands added in later updates.

If you have the Tome of Ultimate mapping, it comes with a full command list, both in the book itself, and as a spreadsheet for easier search/filtering.

I use a projector connected to a computer running a client in player mode. It's easy enough for players to tell me where to move when we are meeting in person anyway (laser pointers are great). I turn on the view following, so the player client on the projector always show the same area as I am looking on in my client (Of course, what the player client actually shows is limited by light, vision ranges, and fog of war of course.)

But most players do bring a laptop. Easier to keep character sheets in an electronic format, and when everyone uses a shared OneNote notebook for note taking, it is easy for the players to keep common notes. So players connect to the vtt if they desire, but it isn't a requirement since we have the projector.

Sometimes when you install the latest update, you may see this error message:

As long as the error message is about the Fcw32.mac file as in the image above, you can safely click ignore here. The error message happened because it failed to make a backup copy of your old macro file. Unless you have manually modified this file (if you are unsure, you haven't), clicking ignore is 100% safe since all that will happen is that the old file is overwritten with a fresh one.