It is no more news that both Telegram
and WhatsApp are serious about ending support for certain categories of devices this year and Telegram have already started implementing it early this year by quitting support for Android devices running Android 2.2, Android 2.3 and 3.0 too. Android 4.0 Ice Cream
Meanwhile, Sandwich is the minimum operating system version required to run Telegram’s latest version.
I believe this move is made to accommodate new features on the Telegram app which older android versions might not support. The same reason WhatsApp is adamant on following suit.
However, if you are a Telegram user or fan still running the Android older version, you can still access your Telegram account via the web from your mobile browser or PC web browser. The same applies to whatsapp users.