To disable your updates, you right click on the Box-Art of the game, which will open up the Quick Menu.


















After this, you press the Properties tab in the menu which will open the Properties Menu.
In the Properties Menu, press the Updates tab, and in the Automatic Updates Section in the Menu, change Always keep this game updated to Only update this game when I launch it.
This won't prevent you from getting the update, but it will let you wait until all your mods are updated for the Anniversary Edition so you wont have to reinstall the game and all your mods from scratch.

There are different methods of backing up your Skyrim Executable, but I will show you the method I used. I used a SKSE Plugin from the Nexus called SkyrimSE.exe Auto-Backup[www.nexusmods.com]
To install this Plugin, you need to have SKSE, and I assume if you are reading this guide you already have SKSE, so no need to explain that as it would make this guide way longer than it should be.

When you download the file, it will be contained in a .zip folder. You can open this with windows without installing any program, but if you want you can install either 7-Zip or Winrar. These are programs made just for opening .zip Files with the only difference being that 7-Zip is open source while Winrar is not.
When you open the .zip file it should contain a folder called Plugins within a folder called SKSE. The Plugins Folder should contain a .dll file in it.
You have to open the root folder of your Modded Skyrim Special Edition and follow what I am saying precisely as this is where you need to install the .dll file you downloaded. Open the Data Folder which should contain a folder called SKSE. In that folder you need to open the plugins folder. This is where you install the .dll file by dragging and dropping the file into said folder.
After this step, open Skyrim Special Edition with the Shortcut you should have made when you installed SKSE. When you load into the game a new folder called auto_backup_executable will be created in your Skyrim Installation. This folder will contain another folder called SkyrimSE.exe_for_(SKSE Version Number), In this folder will be your backed up Skyrim Special Edition Executable.

Congratulations! you have backed up your Skyrim Executable and you have disabled your updates and you are now prepared for the new update! I hope you enjoyed the guide I wrote. This guide is based on the instructions of an SKSE developer named extrwi that said to backup and disable updates for the Skyrim Executable as a way to prepare for the Anniversary Update. Have fun Fus-Ro-Dah'ing in peace fellow Dovahkiin!