From what I have seen on these forums india is kinda different in how it delivers fiber. Most places in the USA or the EU there is a box called a ONT that the fiber hooks to and then you hook up pretty much any router that uses ethernet wan ports.
Many of the fiber connections in india directly connect to the router. This greatly limits your choice. Most of these run some form of GPON for the fiber but each ISP can configure option differently. This means they likely only support a small list of routers.
In this case you are going to seach your ISP site or call them and find the list of routers that work on their system. Now if you have some kind of modem/ONT you can connect pretty much any router to that. Only you can decide which features are the most important.