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

In case you enter a discount code during checkout that doesn't exist or isn't currently active, then you can see the message: “Unable to find a valid discount matching the code entered”.

Normally, most of the websites you can print the grocery coupons from only work on a computer, even you can get coupon books mailed to your home for free. But it completely depends on Amazon's support program at the time you search, so please visit the Amazon site to know more details.

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

Yes, it has ever. It may not be available now, but it is completely possible for loyal customers of Amazon to get it by tracking all of its promotion programs.

It is hard to see a Sitewide Discount of 50% from Amazon on normal days. It's easier for you to shop on federal holidays or important days of the year. New Year’s Day, Thanksgiving, Christmas, Military Day...are recommended.