This gives me concrete generated model, but in array I may have more object for that I will have to add more concrete classes to map the model according to json2csharp. So, I want the solution which is generic for it.
Then you might want to not deserialise the JSON, and just parse it to a JObject instead:
// Remember to add "using Newtonsoft.Json.Linq;"!
JObject root = new JObject.Parse(yourJSONString);
And then use the indexers of root to access the different KVPs. e.g.
root["PremiumStructure"][0]["Level"]
Alternatively, if you want to access the properties with dot notation, deserialise the JSON into a dynamic variable and directly access the properties with that:
dynamic obj = JsonConvert.DeserializeObject(json);
obj.PremiumStructure[0].Level