Q: Is there any way to trace the infeasiblility cause by which equations/constraints ( with =e=, =l= or =g= ), which set by the user, from GAMS when the modelstate = 10, ie 'No feasible integer solution could be found', has occurred?

Most MIP solver do not return a solution at all, if a problem is integer infeasible. If you check the lst file, you will see a messages like:

 RESOURCE USAGE, LIMIT          0.014      1000.000
 ITERATION COUNT, LIMIT         0         10000

ILOG CPLEX       May  1, 2008 22.7.2 WIN 4792.4799 VIS x86/MS Windows
Cplex 11.0.1, GAMS Link 34 

Problem is integer infeasible.

No solution returned

Thus it is not possible for GAMS to provide any further information about the origin of the integer infeasibility. If you have a GAMS/Cplex license, you may want to have a look at “Feasible Relaxation”, which may provide further information. For more details please consult the GAMS/CPLEX solver manual.