@LeZs You should probably reconsider the equipment of choice. For a 3-floor house whith 700m2 garden there's an option to use a Deco whole home mesh system like Deco X50-PoE. For the garden you could...

@sunil012 You can click on downside arrow and check for which router models this guide applies to: It apllies to Archers models from AX, C and A series.

@Emix86 Check the negotiated speed between your main router and the RE700X. This could be done from your main router WebGUI. If the speed is 100mbps that's the culprit. You may change the main router...

@Memo2001 Check this thread. This could be due to the network protection against cross-site request forgery (CSRF) attacks - HTTP Referer Head Check feature enabled by default. Some TP-Link devices...

@chander123 Here's a link to download FW v1.0.16 for EU region. You can do a manual FW update. If your FW region is US (that's on your device bottom sticker) then try this link.

@martri This thread is the best source of information regarding REs Easymesh ethernet backhaul support.