Pickysaurus

You shouldn't be poking about in this folder. C:\Program Files\Black Tree Gaming Ltd\Vortex\resources\app#
The file I suggested you remove was the vortex_deployment.json in the game data folder.
Updating Vortex won't fix this as it's not caused by a bug in Vortex itself. 

You're looking at the rules in the mods tab. The article you're reading is about rules in the plugins tab (Bethesda games only!) 

In the mods tab, use the "Import from..." menu and select Mod Organizer. 
This only works for the main games MO2 supports (and not any unofficial addons). 
 
Kind regards

This usually means your PC's install of .NET is complete borked up. Please see the pinned thread 
 

Click "Suggest" and then "Apply" in Settings -> Mods -> Mod Staging Folder. 
Your staging folder must be on the same drive as the game, but not inside the game folders. 

There are a few other threads like this. You need to update Vortex to the latest version by manually downloading it from the site again. Your version is too old to update automatically. 

You can ignore the errors until Vortex is updated. 

When you update your mod, it's best to hover over "Manage" on the previous version and select "Upload new version" OR put the old version into the field that says which file the new upload is replacing. 
 
If you didn't do this Vortex can't easily work out which file should be downloaded as an update.
 
It's also worth noting that any free user account will be required to open the website anyway. 

Restart Vortex to get any setup checks to re-run. 

Vortex doesn't use API keys anymore, you probably have a super out-of-date version of Vortex, try downloading the latest version and install it over what you have. 

You want all 3 folders for a full backup. If you have to axe one, it'd be the downloads folder. Most mods can be reacquired from the site, but your changes in the staging folder can't be reapplied as easy. 

You shouldn't have the game open when installing mods. If you want to play while it downloads you can turn off the install when the download completes in settings. 

Please see this pinned post for the solution. This error is caused by something being very broken in your .NET 6 install
https://forums.nexusmods.com/topic/12891273-common-solutions-megathread/?do=findComment&comment=124190193
 

You need to pick the top level "Gotham Knights" folder, not the one with the EXE in it. 

This is almost always caused by local security apps interfering with normal certificates. Either than or you need to install the latest Windows Updates on your PC. 

Scroll down the page ever so slightly so see the Download buttons. 

Something outside of Vortex is messing with your load order. Probably the in-game "Plugins" or "Mods" menus, don't open those. 

There is no way to change the default. You can make a suggestion for it though!

You probably removed the appdata folder containing all Vortex's metadata. See this help article for the details on which files and folder need to be move when relocating Vortex: https://modding.wiki/en/vortex/users/migrating-to-a-new-pc

If the downloads don't even start in Vortex (or manually) you should see this page: https://help.nexusmods.com/article/113-troubleshooting-website-issues

As the error says, it's looking for a file with the name in the error, but you have a folder with that name instead (somehow?). Delete the folder at that path and it should fix the issue. 

Reinstalling Vortex will just repair your install of the mod manager, it won't change your mods. 

This isn't really related to Vortex (unless you download direct via the browser and not via Vortex). Please see this guide for help: https://help.nexusmods.com/article/92-im-having-download-issues-what-can-i-do

The solution for this issue is documented here: 
 

The extension developer needs to fix that. They have put 1.1 which is invalid. They need to change it to 1.1.0