Once opened, how long will it last in the refrigerator?

The container states to refrigerate after opening. Use within 4-6 weeks! Do NOT leave this out on the counter, it must be refrigerated.

Can you make it in k cups?

No. This is a latte liquid concentrate that you mix with milk. Chai K cups are powder that you mix with water. There is a chai K cup out there and I've used it but this is SO SO much better. You dump this liquid concentrate in about a half and half ratio. So 1/2 cup concentrate with 1/2 cup milk. After you have this I promise you you'll never want a Chai K cup again.

How much caffeine is in the sugar free version?

I would love to see a slightly sweet version that's ALSO caffeine free-haven't been able to find it! I looked it up, and the product website states "a Slightly Sweet Chai Latte contains approximately approximately 30-35mg of caffeine per serving, which is comparable to a lightly brewed cup of black tea."

has the chai latte powder changed as well as the packaging? I have tried the new designed envelopes for 3 days now the look & taste is lighter.

I only started drinking this a year or two ago, as I was weening myself off coffee; so, I don't know if the taste has changed. However, I like my tea and coffee flavors strong. I use 3 Tbls. of this per 10 oz. p/cup, and also add 1/4 tsp. Blue Lotus Traditional Masala Chai powdered tea to it (it comes with a little wooden measured scoop in each jar). It tastes better to me this way, but everyone's taste buds are different, so you might not like it this way.