Hi @PranayJoshi
First of all, please accept my apologies for late response. We have some backlog with the requests. I truly appreciate that you were so patient.
I will be who is going to assist you with the support, so regarding your first question, it does exist, but it is below a NDA in our website, You may refer to this webpage where you will be able to download the reference manual below NDA by logging in in your account and contacting your FAE:
https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mc...
*Note that this one is the secure reference manual for K81 mcu*
For your second question, the answer is yes, it is supported, but MQX v4.2 is no longer available and superseded by v5. (MQX v5 has a high cost) so I would like to suggest you to use FreeRTOS, due all of our examples based on RTOS from the SDK are developed on FreeRTOS.
Please let me know your comments or questions, it will be a pleasure to continue assisting you.
Best Regards.
Pablo Avalos.