This market resolves as YES upon Twitter being removed from the App Store or the Google Play Store at any point before 2024. Otherwise, this market resolves as NO on January 1, 2024.
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.
Additional context
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.
Fine print
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.
Prediction: it will be walked back. The "removal" of blocking will turn out to be something like no longer being able to block people from viewing your Tweets, which isn't an app store requirement. I don't think Musk cares enough about this to fight his own engineers, much less Apple and Google.