Hi @ReshmaRoy!
Thank you for contacting NXP Support!
The LPDDR can be used by both cores.
The eMMC/Flash memory is needed to boot the processor, Once booted the M7 binary can be loaded from eMMC/Flash memory and run in TCM or DRAM.
To understand better the boot process of the iMX8MP you can consult the reference manual on chapter 6.1 (System Boot).
Best Regards!
Chavira