I’ll try to help you as much as you need, your questions can help others as well. But one thing first : Don’t call me mister, i’m neither that old, nor that formal 🙂
2×25 MHz is not enough as soon as you have more than 2 operators ! What is the solution… use another frequency band. That is the reason why another band, in the 1800 MHz, can be used.
2×75 MHz are available. Plenty enough for 5 or 6 operators.
For your other questions, Navdeep gave you the answers already.
The government can decide to allocate certain frequencies to operator A in one region, and the same frequencies to another operator B in another region. It all depends on your government choices. They can do whatever they want.