Hi Mukesh,
In structural mechanics, proportional loading is referred to cases when the principal stresses ratios and directions remain constant. You can extract stress components of some elements in the region of interest in your model and see if this condition is satisfied.
Regarding the other question, I'm not familiar with Endurica but please see if the training course below on hyperelasticity is helpful:
Topics in Hyperelasticity - ANSYS Innovation Courses
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