Re: Two Questions
If telegram is truly a secure E2E platform
It isn't and shouldn't be considered as such, unless you setup a "secret chat", though even then it's only published details of the cryptograpic protocols used but no code. Otherwise Telegram stores details on its servers, which is one of the reasons why it's so good for multiple devices.
Telegram has drawn Putin's ire because it has repeatedly refused to provide the details for specific users. And it has sucessfully found workarounds round most government attempts to block it, which is why it remains popular in Russia.