If diagnosed with stress and anxiety can the resting heart rate always be higher when standing than sitting or lying down?

I wouldn't necessarily attribute this pattern to stress or anxiety. If you can measure your blood pressure sitting & then standing and determine whether your BP drops on standing, as this would cause a reflexive increase in heart rate to keep the BP from falling and causing lightheadedness & palpitations. In marked cases this is called POTS ( postural orthostatic tachycardia syndrome). ?See MD

Even without stress and anxiety, heart rate is higher on standing than while sitting or recumbent. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.