There is, at least, one known issue: because of something (this issue also appears on the current LIVE version of web telegram), I can't get SMS code by registering of new user. It don't come at first attempt. For the second attempts and next, you will receive an sms, but it will be invalid. Because of this, you will not able to get to crop avatar screen.
Explanation: if you are existing user, it will redirect you message page, if you have 2FA pass, you will enter it first. But if you are a new user, you can't have a 2FA password so this screen will be skipped, and you should be redirected to profile page.
And how you could to suggest, I wasn't able to test this screen in live conditions, only for mocks.
The main work was done for login/signup flow. Because of that, the messenger screen a bit ugly.
But, there is a need code for this, for that case, if this will be possible.
The issue is relevant for all webogram based apps in this competition.

I've found a way to check an avatar screen, but with the next way, the back-end part will be unavailable (it should be fine, if you was able to get SMS code earlier):
1. Go to developer tools;
2. Go to source: ./features/Router/utils.js;
3. Trying to make a breakpoint for line 6. It will be set you on row 4. Right after `step = `, before `(` symbol;
5. Find `goToPersonalDetails` function in the `scope`.
6. Click on this by right mouse button, and select `store as global variable`.
7. Run code;
8. Call this function in console. The name should be `temp1` by default in the Chrome
Enjoy!
P.s.: if you will able to get this screen with auth data, you can change avatar.

Total spent time: 106h

I've found a workaround (solution?) concerning the issue that I said above. The workflow is fixed locally yet.

Качество реализации процессов логина ниже ожидаемого.
В приложении некорректные ограничения на количество символов в номерах некоторых стран, некорректно работает поиск по странам (например, не найти Lithuania, United States).
Критично, что приложение может отображать ошибку 'Invalid code' на экране выбора номера, ограничивая дальнейший лимит символов в номерах до шести.

The "NEXT" button doesn't appear after entering the phone number.