Install custom system, on unlocked bootloader I have buy a china device. and i will install custom ROM / system
Name of Phone:

MYCELL i11 pro

ebay: https://www.ebay.com/itm/i11Pro-6-1-8GB-128GB-Smartphone-Android-9-1-Dual-SIM-Mobile-Cell-Phone-Unlocked/402019064450?ssPageName=STRK%3AMEBIDX%3AIT&amp;var=671879680646&amp;_trksid=p2057872.m2749.l2649

I have unlocked the boot-loader
And i have take backup of ROM/Firmware.

I use (SP_Flash_Tool-5.1916_Linux) to flash new system.img.
But then i do that i got stuck on boot logo, then i flash back to official ROM, so i can run the phone again.

My question is how i can install another firmware to the phone.
Any one can help me ?

Thanks for your time
I got it to work with install another system on the phone !

Model phone MT6570

step 1:
Download: https://www.needrom.com/download/blu-studio-j2-s590q-2/
step 2:
Format the hole phone (with MT6570_Android_scatter) from step 1
step 3:
Load the new (MT6570_Android_scatter.txt) from the step 1
step 4:
From the real Firmware (https://www.needrom.com/download/i11-pro/)
step 5:
Change the real preloader, lk, boot, recovery, logo, md1img, secro, cahce, userdata
step 6:
Load the system.img from step 1
step 7:
Wait for boot up


Hope the helps other :)

It works for me !