Hello,
For experiment purposes, I did the color of the Kernel boot logo which stored in the kernel folder. After compiled & build the image (Android 9 box ) and flash the image into sd card.. then we booted Rpi4 with the new image then we have seen the updated colored kernel logo 
then android animation started but the animation not ended afterward 
Please note we have not modified Andriod animation.
Did any faced this issue before ?? or I missed something here
I think the kernel logo can only be 255 colors max.
Try to convert the image to have max 255 colors.
There are logo_kernel.bmp and logo.bmp.
If you don’t change both, remove one of them.
If the bootanimation doesn’t finish then it means the RockPi 4 image you use is not suited for a different RK3399 device and you can’t do anything unless you get the SDK from that manufacturer and build firmware from it since RockPi 4i 4 has very different components compared to other RK3399 devices.