among halogens, the radius ratio between iodine and fluorine is maximum because iodine have maximum radius while fluorine have minimum radius.

And due to highest radius ratio rule maximum numbers of atoms are present in iodine fluoride.

Interhalogen compound are more reactive than halogen compounds because bond between them is easy to break while the bond between X-X is very strong and cannot be dissociated easily. Hence (ii) is incorrect

Hence the correct options are (i), (iii), (iv)