How to implement such a scheme?

Question

proxy

- It is necessary to connect the modem to the browser (network settings --> connect proxy)
- One, possible, implementation option. Modem --> some device (computer, router) --> Internet --> VPS --> browser (connection via proxy).

Answer 1

Limitless IP addresses.

If you mean quantity, then it doesn't happen.
If you need different browsers to access a certain resource with different source IP addresses, use a proxy or ssh tunnels (essentially through a proxy).