@dravidham
Some devices are capable of seeing a map .img with <any-name> in a folder named either Map or Garmin on sd card. Certainly your nuvi 265 is not one of them however from memory the nuvi 1xxx range can. What is certain is that both of them can see a file named gmapsupp.img in a Garmin folder on a card i.e. x:/Garmin/gmapsupp.img because that's universal for any garmin device with a card slot.

As said the so-called "4GB limit" is a FAT32 limitation and it's 4 gibibytes minus one Byte. As GiB is binary that's a factor of 1024 being used so the limit is 4,294,967,295 Bytes: (4 x 1024 x 1024 x 1024) -1. However GB or gigabyte is now considered decimal, a factor of 1000. So a 4GB card theoretically has 4,000,000,000 Bytes available, at least it should nominally. In fact it's even less because some space is used up already for hard-coded information but regardless the full EU image cannot fit so you need a bigger card. Windows OSs unlike Mac and Linux still report GB as it's original binary interpretation not decimal further adding to confusion.