Is this gluten free?

There don't seem to be any ingredients that contain gluten. The ingredients are:
ORGANIC TOMATO PUREE (WATER, ORGANIC TOMATO PASTE), ORGANIC DICED TOMATOES (ORGANIC TOMATOES, ORGANIC TOMATO JUICE, NATURALLY DERIVED CITRIC ACID AND CALCIUM CHLORIDE), ORGANIC SUGAR, ORGANIC ONIONS, ORGANIC OLIVE OIL, SEA SALT, ORGANIC SPICES, ORGANIC GARLIC, ORGANIC DEHYDRATED ONION, ORGANIC DEHYDRATED GARLIC

What is the shelf life of unopened containers?

At least a year

How long are the jars of unopened sauce good for?

The expiration date will be at least a year away or more.