You can prevent windows 10 from downloading updates using registry editor Regedit.
Warning: Editing the registry is risky and can cause irreversible damage to your windows if not done correctly. Thus don't forget to take full backup of computer before proceeding [Tech2Craft is not responsible for any damage]. Following are the steps to Stop automatic updates.
1. Press Windows key + R key simultaneously and open Run command.
2. Type regedit and click OK to open Registry Editor.
3. Now browse following path: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows
4. Right-click the Windows folder then hover mouse over New, and click Key.
5. Name the new key WindowsUpdate and press Enter.
6. Now Right-click the newly created key and hover cursor over new, and click Key.
7. Name the new key AU and press Enter.
8. Inside the newly created key, right-click on the blank space on right side, select New then click on DWORD (32-bit) Value option.
9. Name the new key AUOptions and press Enter.
10. Double-click the newly created key and change its “Value Data” to 2.
11. Click OK and close Registry Editor.
Also You can input any of the following value in “Value Data” field mentioned in Step-10.
• 2 - "Notify for download and notify for install."
• 3 - "Auto download notify for install."
• 4 - "Auto download schedule the install."
• 5 - "Allow local admin to choose settings."
Best choice is to change the value to 2 as it configures the "Notify for download and notify for install" option on your system. Thus by using this value prevents Windows 10 from downloading updates automatically, and you'll get a notification when new updates are available. Thus after tweaking, Registry Editor with this little trick you will get notification when updates are available, and you can manually download the updates but updates won't download and install automatically.
We do not recommend using a computer without the latest updates, because they're often aimed at keeping your Windows 10 PC running safely. However, there will be times when you may want to manually apply new updates, when you want to install them in your convenient time, or because you want to wait until you're sure the update will not cause issues then you can definitely use this trick.