How to make my cellphone a router or a hotspot thing with a constraint
You can turn your device into a Wifi Hotspot (there is an option in the general settings, usually with the other connectivity settings).

Generally, you will need to pay your Cellphone provider to allow you to use this particular feature (although there are ways to get around this - but that is another thread).

Bottom line, there is an option in the settings - if your phone can support this, you will easily be able to turn it on.