No, deleting Telegram does not delete everything. You can still find your chat history in your phone’s “Chats” app even if you’ve deleted the Telegram app.
Yes, your contacts will know if you delete Telegram. If you have a contact list with a lot of people, it may take a while for them to notice that you have deleted the app.
When a user deletes a message from their device it will still be stored on the server. When the user deletes the message from the server it will still remain on their phone. If you were to delete a message from both your device and the server, the message would no longer exist in either place.
Deleted Telegram accounts will look the same as a normal account, with the exception of an option to delete the account. A deleted account will show up as one that was never created on the app, and cannot be accessed. Deleted accounts are not automatically removed from use, but can be done so by any user who was added to the group chat. With only one person holding the access to this feature, it may not be possible to remove them from the chat without their cooperation.
Telegram is a messaging app that operates on a subscription-based system. Telegram offers a basic plan of $0.99 per year to allow for unlimited, secure, and private messaging with the possibility of adding up to five other chat participants into one group chat. Other plans are available at different rates if more chat participants are needed or if an individual user wishes to pay for specific features.
When you delete and reinstall Telegram, all of your chat history will be lost. You’ll have to start over again on the new installation.