Here is the latest update:
I was able to install the OS(not in UEFI mode). The UEFI mode is still stuck at "Still waiting for root device". Hence, I installed the OS in legacy mode. The installation was successful. Although I am facing few other issues now.
Graphics: The display is showing resolution as 1024x764. Although my native screen resolution is 1920x1080.
Trackpad: Trackpad is behaving weirdly and sometimes is not responding.
Coming to other things:
Sound: Working
Battery: Working
Keyboard: Working
WiFi: Un-supported Intel card(Will be changing the card once the install is stable)
I now want to install clover on my installed HDD(Without breaking the installation) and fix the Graphics and Trackpad problems. I am fine with booting the OS in Legacy mode as the UEFI is still stuck at "Still waiting for root device' even when booting from installed HDD(using the bootloader from USB). I am attaching clover zip(F2 + F4) and "About this computer" Screenshot. Tell me in case you need any other files. Thanks again
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One idea in my mind is creating USB installer in Mac now that I have working(somewhat) OS X machine. But I want to know if this will help in any manner.
Edit: I am booting after unchecking "Inject Intel" in clover boot options. Without doing this the system is booting to blank black screen.
PS: I have done DSDT and SSDT patching in the past and i am comfortable in patching using your laptop fixes