 upon Twitter being removed from the App Store or the Google Play Store at any point before 2024. Otherwise, this market resolves as 

Inclusive "or" - if Twitter is removed from both simultaneously, this market resolves as YES.

"Removed" = can no longer be downloaded, even if the app's page is still accessible. 

I'll resolve this as YES only if the Twitter app is removed from the App Store and/or Google Play Store in a country where the app was accessible and downloadable at any point on August 18, 2023. 

Several of Musk's proposed policy changes, and in particular the removal of the blocking feature, conflict with the Terms of Service of both the App Store and Google Play Store. Were he to go through with these changes, the app could be delisted and made unavailable to download.

I call it Twitter and not X out of habit and spite. This market still resolves YES if "X" is taken off the App Store or Google Play Store.

The length of time the app is unavailable to download doesn't matter - but it must be because Twitter specifically is removed. If the entire App Store is down, that doesn't cause a YES resolution.

The app can be removed for any reason - it doesn't have to be because of a decision Musk himself made.