@Bshara If you want to go further and avoid the double NAT in your LAN (from introducing the VR400 as a second router), you can follow this guide and use the VR400 as an AP. The cabling in that case...

The device is under warranty, why don't you contact the retailer or if he can't assist you, approach your local support for a resolution.

Not sure about Archer A7, but some devices won't flash the FW file if it's not newer than the current one. Also you can't upgrade with FWs from a different region or HW version.

@Osama-Orabi You can see more detals here. I would say that these messages are normal, cause sometimes PPPoE session drops and has to be re-established.

@Osama-Orabi Exchanging DHCP server messages between your ADSL/VDSL modem and your devices connecting to it - IP address offer and acknowledgement. Also exchanging some PPPoE authentication messages...

According to your device FW version you're on the latest. Here's the official versions. If you suspect strange device behaviour you can hard reset (methid 1) the device and try again.