How can I create a must-see ad video to my application?

Hello there,
How can I add a video ad that users have to see in order to move to the next screen? I'm not talking about the banner ads. I need a must-see video ad. After Watching the video the next screen opens.

.... Disable the button that takes the User to the next screen, enable it when the video has finished.

but what if the user is using the app offline? Will the app work?

Ads will not load in offline, but all other process works normal even online or offline

If the ad video is stored in the App the video will work off line. How big is it? Are there many or just the one? Does the video belong to you (no royalties to other parties?).

If the video fails to run (which it shouldn't), that's going to present the User with a blank screen for the video duration. However, if we can detect a no-play, we can enable the 'next' button.