But I understand, why this laptop can ASUS supported for Windows 7...... Drivers are available for W7, W8 and W10
Reading what I wrote above can help you. There isn't any need to use the w7 bootloader to use win7, just use w10 one's and live long and prosper.
That will not work. It might start booting & then die, as Win 7 CAN NOT be installed on pure UEFI with no CSM support. End of subject
Create a suitable VHD (not VHDX which isn't supported by win7) using w10's disk manager, 16/18GB should be more than enough for a quick test. Deploy win 7 on it. The easiest way is using gimagex, which is graphical. Be careful to apply the right image from install.wim (there are many from windows home premium to windows ultimate, use the info tab to get the right one). Install easybcd and add the W7 item to your bootloader. Done. Reboot ant test if it boots. I can't guarentee it works, but the whole operation requires really 5 minutes, so no much wasted time anyway.