Why cant it be used on the whole shoe (outside of soles) ? States not to use where the shoe flexes or creases??

Mirror shine should only be used or the hard countered parts of the shoe(different on different shoes). This is because the soft parts of the shoes bend and when they bend the hard wax will flake and create an unsightly white look. Use soft cream polish like Pat de Luxe on these parts.

Which color choice should I use for some dark chili colored shoes?

Saphir mirror gloss is very expensive, so I only use it on the toe caps. I don't think the tint really makes much difference; I use the clear on all my shoes, no matter which color they are. For the rest of the shoe, a lower cost tinted wax or cream.

What is the quantity in the can...75 ml ? Ml usually used for liquids....what is the mass of this product? Grams or oz ( dry weight)

This item is measured with volume. I don't recall exactly but 100ml sound right, regardless this will last many years. its a hard wax and very little goes a long way. Its a little nuts how good this wax really is and wouldn't use anything else. I also have the cheaper wax and I use that for sole edge.

Want to add shine to my lambskin bag. Anyone tried this on bags? does the shine last?

It depends on the construction of the bag… if the bag is stiff yes!!! If it is softer Pat De Lux would be better. If it is very soft, use cream polish only. I use the full range on my shoes. For flexible side and vamps, I use cream polish and small amounts of Pat De Lux, for stiffer areas, Pat De Lux Gloss, for toe caps and heel counters I use mirror gloss.