for a spouse visa..
you need to be in the uk 2years (- up to 28 days) and pass the life in uk test before you can apply for ILR, and after having ILR for 1 yr you can apply for citizenship.
if you cannot apply for ILR because your visa will expire b4 you have been in the uk 2yrs (- up to 28 days) or you cannot pass the life in uk test in time, then you will probably have to apply for FLR, which might last til you have been in the uk 2yrs or for up to 2yrs if you could pass the life in uk test![]()