How to set up the distribution of wifi through 3-4g?

Question

WiFi

There is public wifi, how to connect to it remotely via mobile network? this is how the modem distributes 3g over wifi, you just need to distribute wifi over 3g,
Let's say I flash the modem, leave it in the wifi zone and I can connect via 3g to the modem from anywhere and go online already with wifi The point
is that it will be like some kind of proxy, don't ask why, you need it that way

Answer 1

Yes it is possible, routing and VPN. Through 3G over VPN to a common network, then on the basis of this network, route traffic through that wi-fi. Naturally, the device that will be in the wi-fi zone must provide routing from the VPN network to the wi-fi network.