@EugenStanis, thanks for your help.
I connected device, ADB on, Rooted and typed the commands.
A window opened in PC (Win 7) which says:
Qualcom USB Composite Device9091 .... Ready for use
Qualcom HS-USB Diagnostics 9091 .... Ready for use
Qualcom HS-USB Modem 9091 .... Ready for use
Qualcom HS-USB WWAN Adapter 9091.... Failed
ADB Interface .... No drivers found
Install both apk's on your mobile (com.oem.oemlogkit_1.0-1.apk and com_android_engineeringmode_V1_01.apk)
Disable driver signature enforcement: https://windowsreport.com/driver-signature-enforcement-windows-10/
Reboot PC. Install driver: QUD-setup_op7ready.7z and QPST_2.7.474
install this: https://forum.xda-developers.com/showthread.php?t=2317790
open dialer app and enter *#801#
Set Serial and Full-port switch to ON
Reboot and look if Serial and Full-port switch is ON. If not, check it again, launch Minimal ADB and fastboot then
setprop sys.usb.config diag,serial_cdev,rmnet,adb