SITL simulate one motor off HELP!


I have some questions about the SITL because i have encountered some problems while using it.
Indeed, i am simulating an hexacopter and i would like to be able to stop one motor to see the behavior.
Firstly, what is the correct behavior i should expect to see? Does the copter 3.6.5 version can stabilize an hexacopter with one motor off? or only octocopter

Secondly, after i use the SITL parameters SIM_ENGINE_FAIL XX and SIM_ENGINE_MUL 0 with XX the motor number i want to stop, the drone fell and crashes.
In my log of RCOUT values, i can see the XX value goes to its minimum and one other motor going to its maximum while the 4 others start oscillate. Is it normal behavior?

Does the SITL has bug with those parameter?

Thirdly, what is the difference with SERVOXX_FUNCTION 0 and SIM_ENGINE_FAIL?

Sorry for long post and thank u in advance