Control ESSP8266 IOT board over cellphone hotspot wifi
This is not exactly an electronics question, rather a networks one.

To put it simply, when connected to a router (here, your phone), a device has a private - or local - address, which you use when connecting with devices also using your phone's hotspot, or network. They are usually between 192.168.0.0 and 192.168.255.255 or 10.0.0.0 and 10.255.255.255. The private address is usually provided by your router, via a DHCP server. 
To connect to the internet and browse websites such as stackexchange, you need a public address, which is provided by your Internet Service Provider (ISP) to your router. When accessing the Internet, all of the devices connected to the same router will send requests to the router, which will then forward the request to the Internet. As a result, all of the devices connected to the same router will access the internet with the same public address.

This means that you can't access a device via its private IP with another device on another router, because they are completely different networks and one's private addresses don't mean anything to the other. By creating a hotspot with your phone, you created what is called an intranet. As it is, you can't access it with its public address either, because there are several devices on the same address, and the router won't be able to know which device you want to connect to if you only use the IP address.

In your case, you won't be able to access your board from another network, as cellphone networks are restrictive. However, if you have a home network (not your phone but a regular ISP), you might be able to setup port forwarding to access your device from other access points, with the public address of the router. However, the exact procedure is different for each ISP so you will have to do a bit of research.