HELP please, would being sedentary & sitting cross legged (Indian) most all day cause Plantar Fasciitis?

Stop wearing the flip-flops. Get used to the orthotics by wearing them a couple of hours each day and then increase the time by an hour or two every few days. New Balance is a good shoe recommended by many podiatrists and consumers, so wear them. Start walking up the block and back each day, increasing the distance each week. Since you admittedly have constrained them, your muscles and connective tissues need to re-learn what they're supposed to do. Incorporate some light stretching before and after your short walks (a link is below). Soak your lower body in a hot epsom salts bath before bed for a few nights as you begin to get active again. After a few weeks of your new regimen, go back to see your doctor. From personal experience, I can tell you that if you don't use it, you'll lose it. You can either do or sit and complain. Your choice, and your quality of life.