Need help with ender 3 v2 firmware update for several upgrades

Hello everyone,I am pretty new to 3D printing having got an Ender 3V2 for Christmas. It’s a Creality Ender 3 v2 with v4.2.2 motherboard.In summary i need firmware that supports increase in max temp for all metal hotend upgrade to 270 degrees, the BLTouch levelling and increasing bed size X&Y to 400mm.I have made several upgrades that require firmware updates but have no idea how to do them.My first upgrade was adding BLTouch and I managed to download firmware that worked ok.I have since added a micro Swiss direct drive system and an ender extender 400, increasing both X and Y to 400mm.I have seen a confusing video on YouTube about downloading something from GitHub and changing stuff in Vcode but it appears out if date as some of the labels or variables cant be found in the config or pins files.Any ideas really gratefully received.ThanksS.