Student or Learner
1) The WI-FI internet network only cover a limited range.
2) The WI-FI internet network will cover only limited radius.
3) What is the range/radius of the WI-FI?
5) How much range/radius can the WI-FI cover?
It doesn't 'cover a range'; it has a range; or it can be said to have a certain coverage.
Incidentally, parts of the internet are based on WiFi; a WiFi network can connect to the internet. There is not now (and I think probably never will be) a 'WiFi internet network'.