if no ISSU, I dont see a reason why you have to jump between those, you can just change the bootvariable to 6.2.8. 

Those are different things. Policy type qos  --> Function: Define traffic classification rules -->attached under System qos and Ingress Interfacepolicy type queuing -->Function: Strict Priority queue & Deficit Weight Round Robin --> attached under: S...

what is the reset reason in show version? 

you cant do ISSU with single SUP, backup ur configs on bootflash, change the bootvariables and reload.

That is very broad problem, you need to narrow it down a little bit.Can you attach a topology of N7K and 6500? then would start from there.