My goal is to make a website, in which user could customize a photo and then provide his friends indicators like name or id. My next task is to fetch that info from database and send messages on specific date to provided users. Ex birthday wishes, greetings, and so on.
I studied facebook send api for a few days now and couldn't find solution for myself. If I want to send message, I need to have Page-scoped id of user, which is acquired when the person text you first, which is not desired, because person wouldn't know what it is.
Also I was looking into Customer matching API, also seems to require the same PSID. The next thing I checked was Send Dialog API, which seems to send messages instantly, but not on the specific date. Also I checked unofficial facebook-chat-api, which asks for user ID, whereas I can find my id, I couldn't find ids of my friends.
So I just want to know is it even possible, if yes, I'd really appreciate your help.
User to User communication is not possible (and not allowed) in an automatic way, there is no API for it except for the Send Dialog. The Messenger platform is for page to user communication only.
Do not use inofficial tools, they are not allowed and might get you banned.