is there is a way to downgrade the game from 5.4.8 to 5.4.2 ?

as title say is there is a way to do that bcuz i dont need to download the hole game again it will take 1 week

You only need Wow.exe from 5.4.2. Put it in your WoW folder and it should work. You can use the torrent from download page and select only Wow.exe.

Thank you :)