Normally, the military discounts programs on some occasions of the year. In order to know whether it is offered or not is depended on Viatao's policy sales, you can visit the store now for your reference.

Discount codes don't stack. If you have 56% off discount, they can't also use a "free shipping" coupon since Only one discount at a time can apply to a single order at the Viatao site.

Of course not, most coupons may be used only by you when you received them directly from Viatao. As the Viatao coupon includes your User ID, it cannot be resold or transferred in any way.

Usually, Coupon Stacking is not allowed at Viatao. However, the store will surely give out notice if available.