I'm wanting to buy this product but why is there no nude color offered??

I use that shade and the color seems to adapt to your skin color. It’s much easier than trying to find the exact shades you need with other foundations.

I can only use physical sunscreens. Which sunscreen ingredients are used in this product?

I am actually wearing this BB cream right now! It's really good. It says that there is erthylhexyl methoxycinnamate/octinoxte 3%, titanium dioxide 6.28%, and zinc oxide 1.92%. I don't know if that helps but that was what is on the tube.

Will this product work with a white-white complexion?

Yes. It works with all kind of skin. Go to Google and check the product

Do you need to use the product within 6 months of opening the tube?

The product labeling and instructions DO NOT indicate the time frame within which the product must be used. It does not indicate an expiration date or a manufactured/packaged date. With my tube of this product, I treat it like any of my cosmetics - I make sure that my hands or applicators are clean prior to touching the product container (or avoid touching the opening of the container to avoid contamination), and I observe the consistency and quality and smell of the product to see if it has changed (would indicate aging of it or bacterial contamination), and I would toss the product per my discretion if any of the above is observed.