BTW, about Telegram Bots Platform, in past I wrote some thoughts about it:
As developer myself, I experienced Telegram bot API API usage and I’m happy regarding some technical aspects (supporting some long-term visions…).
Anyway, maybe I’m wrong but right now Telegram is almost the only one mainstream instant messenger chat app that support bot API “for free” (without any restriction to all the people);
this is a collateral but relevant topic for me: implicitly, Telegram bots are a sort of social experiment allowing everyone to set-up a bot for any goal… and in facts now Telegram bot implementations are now often just a bit more than useless games (is what you named “education stage”, and I named in my article: “generation 1” aka “command based”): poor or not NLP at all, non user personalization, no real usefull services/business behind.
In contrast, as you remind, Facebook Messenger right now have a “closed” model, giving SDK just to a very short list of third parties companies (Uber, and a bunch of big brands).
That’s what I’d call “company-centric” business model. Slack is something similar…and Chinese Wechat is the big model many are copying now (without admitting openly) ;-)