I am running the system GMM model in my study, what I need is to know the interpretation of all specifications in this model such as
1- Arellano-Bond test for AR(1)
2- Arellano-Bond test for AR(2)
3- Sargan test of overid. restrictions
4- Hansen test excluding group.

in addition, when I can report my results? other words what is the significance level that consider as a good result for the four specifications above?

one more thing, is it necessary to add the lag of dependent variable into the model used in the study?
thanks in advance