How should I upgrade Windows 10 Version 1709 in my laptop, to Version 1809? Assume that I do not want to format my laptop and perform clean installation of Windows 10, since it is an office laptop. Thank you very much for your explanation.
#1. Get 1809 Refresh ISO with language and architecture matching the system installed on your laptop. #2. Create backup of old system (recommended). #2.1. Disable or better uninstall 3rd party Antivirus (valid addition by @pf100). #3. Mount the ISO and run setup.exe. Follow the screens, it should offer to keep programs and settings. #4. Start process. #5. hold your breath and pray to your gods...
In addition to what you said, I always disable/uninstall antivirus/antimalware (except Defender) before #3 mounting the ISO and installing. I've had a couple of ISO installs not work until I did that.
I have found that it wouldn't upgrade from the .iso files until I disconnected from the internet. I never understood why but after I did that Windows 10 build whatever would then upgrade.