Goto your facebook homepage or Groups or Pages and pause on any Video or Play it. and you will find 2 buttons below every Video to Download in HD or SD Quality as MP4. See screenshot below.
Go to. any single video and you will find 2 blue buttons upper left on every video and you can also download the videos on HD or SD Quality as MP4 See screenshot below
Also you Will Find the download links on any streaming Video like the below screenshot