Generally if all your documents are in order you should get a 3 month entry visa. I can’t say for sure but if you are using an agent then they know the system better.
In my situation I had to return 3 times before they accepted the documents. I didn’t use an agent in the process. My immigration office are stringent.
when you say start your marriage visa have you already provided all the documentation required?
The process I went through is make an appointment provide all the required documents this gets you 90 days. Then come back before the 90 days and provide all the documents again and then you get the under consideration stamp. Finally at the end of the under consideration you get the 1 year extension.
sorry I wrote my 90 day expires 11 April that expired 31 March. My under consideration expires 11 April. So I can’t go until that date for extension. Ok thanks.