Complexity: Working directly with MTProto is significantly more complex than using the Bot API.
Authorization:
Privacy: Even with the full API, you will still be limited by the user's privacy settings. You won't be able to access information they have chosen to keep private.
Finding Your Own User ID:
You can easily find your own Telegram User ID using the userinfobot bot. Simply start a chat with it and type /start. The bot will reply with your ID and other basic information.
Finding Other Users' IDs (Limited):
UserInfoBot: If another user sends a philippines telegram mobile phone number list message in a group you are both in, you can forward that message to userinfobot to see their User ID.
RawDataBot: As mentioned in the search results, you can use RawDataBot to find the Chat ID, which for a direct chat with a user is the same as their User ID.
Important Privacy Considerations:
Telegram prioritizes user privacy. You will not be able to access information that users have intentionally hidden through their privacy settings using standard API methods.
Any third-party tools or services claiming to provide access to hidden information are likely scams or violate Telegram's terms of service.
In summary, while you can get some user information by their ID using the Telegram APIs, the extent of the information you can access is limited by the API you use and the user's privacy settings. For most users, the easiest way to find their own ID is via the userinfobot. Getting information about other users by just their ID without prior interaction or their consent is generally not possible.