Please note that Telegram X for iOS has been discontinued. Its code has been merged with the main Telegram app. Please download it from the AppStore to get access to new updates:
https://itunes.apple.com/app/telegram-messenger/id686449807
The new Telegram for iOS has all the features of this old app – and more, including Archived chats, advanced privacy settings and animated stickers.
Telegram for iOS also supports multiple accounts (try Settings > Edit > Add Account) - and if you're a fan of the black icon, you can choose from several versions in Settings > Appearance.
Thank you for helping us test and develop Telegram X. Note that Telegram X on Android is a separate project, it's not going anywhere.