The prepositions in, on and at have similar meanings . However , they are used in a different ways. They are used before places.
Generally, in- used before large places such as a country, State, city, town and a province.
However, when you use a big and small places together , use -in- for the bigger place and -at- for the smaller place. For example: I live at Mumbai , in India.
When we use it as a prepositional phrase : We should use :in a park, in a hotel, in a car,in a room .
On- It is usually used before place which are neither too big or too small . Example- street, road . It is also used before : a ship, a train, aircraft.
At: It is used when you mention the exact door number of an address. For example:
At - is also used for location. For example : I am at the airport. We use 'at the airport'because the airport has a very wide area and you are not specifying the exact place.
When you specify the exact place where you are stationed say - ' I am in the check in area.
I live in India.
Please keep the parcel in a corner.
I will call you later , right now I am in the car.( car is a small place) But, I am travelling on a train.
My friend is at the railway station to see of his mother.
I am in the college canteen.
I stay at 55, M.G.Road in Bangalore.