I didn't finish reading the whole thread, so idk if you actually found out but I'll spill it anyway lol
When you boot to recovery and get the "No Command" thingy, just press the Power key first then Volume up (while still pressing the Power key), and you're in the recovery! Simple as that.
After you boot into twrp using fastboot, twrp will open. Then you need to flash twrp installer, then boot into system. Then open twrp and install SuperSU sr5 version. Boot into system and check for root. If you want to hide root, open twrp and flash suhide 109. Boot into system and use suhide correctly, open apps and clear cache & data from play store app, clear cache from play services.
You should be certified.