Hi I was wondering if there might be an answer key for Ticket 10 some where I could see.
It is not on the Solution Guide.
SW3 and SW4 are doing Q-in-Q tunnel for R4-SW2 link, but system MTU=1500. I changed it to 1504, but not sure if it's right solution
That is correct, the MTU should be changed to 1504 to cope with the extra dot1q tag. Your solution is correct.