What is the ruling on buying, selling and eating sturgeon?

Recently a documentary showed chicken runs in Pakistan where blood, veins of animals and meat of animals not slaughtered according to sharia are given as food to chicken. It made people worry as to what is the ruling on consuming such chicken? Is it permissible or not?

Is it a sin to look at the photo of a painting which depicts an imaginary woman in nude?

Some stores sell frozen fish. Is it permissible to buy and eat such fish?

Is consuming white alcohol, which is advised by physicians for heart problems, permissible?

In some restaurants, for example McDonald’s, where fish is served to customers, it is not known whether the fish is of the type that has scales. In such a case, is there any problem in eating the fish or not?