Use APKPure App
Get Unread It - Unread any SMS old version APK for Android
Mark any SMS as Unread, Even after you've read it. Now Works for Kitkat+ also.
Don't want your Girlfriend/Boyfriend to know that you've already read their SMS? Then "Unread It" is the Ultimate destination.
Now mark any message as Unread.
Now Works for Kitkat+ also.