Two parts to this question:
1) Say a person is providing a wireless hotspot to me as I have no internet, when I access the internet what is my IP address set as?
--> Some companies basic level of fraud detection I assume is that the geographical location of the IP address is nowhere near the location of the IP of the device accessing whatever service it may be. So if you were on a mobile device accessing a site from a geographical location similar to the usual device, would this bypass this?
2) How can you find out the IP address of your device when on a hotspot
Say a person is providing a wireless hotspot to me as I have no internet, when I access the internet what is my IP address set as?
When a person connects to a wireless hotspot, two IP addresses are set i.e. a Private IP address and a Public IP address. The wireless hotspot automatically allots the requesting device a Private IP address from a range of available IP addresses which is unique to that device. The device then connects to the internet via a Public IP address.
To break this down, when you turn on Mobile Hotspot, your phone's WiFi adapter turns on the router mode. Now the IP address is assigned by the wifi adapter running in router mode. In stock Android devices the default IP of your phone will become 192.168.42.1 and subnet mask of 255.255.255.0. However, this might change.
How can you find out the IP address of your device when on a hotspot?
In Windows, use ipconfig in cmd. Look for Default Gateway under your network adapter for your router's IP address. Look for IPv4 Address under the same adapter section to find your computer's IP address. Replace ipconfig with ifconfig in linux.