Is it permissible to obtain a guardianship deed from the court for the purpose of getting a health insurance card for my mother, and am I truly her guardian?

The son must take care of his mother's affairs after the father's death, and he takes precedence over other guardians, even if her own father is alive. There is no religious impediment to obtaining a certificate from the court proving his guardianship over his mother and his management of her affairs. As for health insurance, it is not permissible unless it is cooperative insurance.