What information about the user and the mobile device can be found if the device is connected to the Internet through my wi-fi router with a 3G SIM card?

Question

Android

Connoisseurs, tell me, please, what can I learn about the user and his device if it is connected to the Internet through my wi-fi router with a 3G SIM card?
Example: A person is sitting in a cafe. connected from a smartphone to my free wi-fi, distributed from a 3G router. What information can I get about it? (Device brand/model, OS type, what applications/programs are installed, which telecom operator, geographic location, what sites you visited before (before connecting), which sites you are currently on, etc.)
And is it necessary to obtain this data somehow program the router, add some software or something else? If yes, which one?
Thanks for the help!)

Answer 1

The question reeks.
Why are you giving access to your router? Specifically, to find out "Device brand / model, OS type, which applications / programs are installed, which carrier, geographic location, which sites you have visited before (before connecting), which sites you are currently on, etc."?
This is not good.

Answer 2

Attention! The information below is provided for informational purposes only. Depending on which country you live in, this may not be desirable, illegal, or very illegal.
0) Download Wireshark . You put it on a laptop for example (nothing needs to be done with a router). Wireshark intercepts traffic. You analyze it (in real time or save it to a file and do it later).
1) Find out what sites the user visits.
2) Most programs periodically communicate with the network (update, send statistics, error reports) - you analyze and find out which programs are installed by the user.
3) From the analyzed traffic, you will find out the mac address of the device, ip address, and so on.
4) If the user is on https sites, doMITM ( Man in the middle ) and you can access the data that the user sends over https. You can use SSLstrip or Intercepter NG
I don't know much about routers, but I don't think you can install your own firmware on it. It also depends on the model. If you know that you can install OpenWRT on it , then you will have even more opportunities not only to intercept traffic, but also to carry out various attacks.