firmware update question

Internet has been behaving funny last two days. I reset the modem and called my internet provider who did not detect a problem. I checked in the Orbi app for firmware updates and it says I am up to date (ver V2.5.2.4) . However, I went online to the Negtgear website and it lists a much different firmware as the latest version (v2.7.60)

So, I downloaded this update , I opened the zip file which contained an *.img file. When I double clicked, it would not mount and it returned an error message (*"couldn't mount") . I am updating through a PC (win10)

2 questions:

1) How come the phone app disagrees so much with the firware avaialbe in the website? which one is the latest?

2) if I am dowloding the firware, why can't I open the img file? is there a more Windows friendly format?

Thanks

SG20

https://kb.netgear.com/000062494/RBR50-RBS50-Firmware-Version-2-7-1-60-for-US-Region-Only