you could write pages on this topic. However, a short answer with respect to the situation in Europe, i.e. under the EPC:
Situations 1 and 2 are identical, since a method claim can not be dependant on a product claim (different claim categories, i.e. per definition independant). Requirements for patenatibility: in a claim to the product the product should be novel and inventive. In a claim to the process, the process should be novel and inventive, but the product may be a known product. For scope of protection, the product claim offers the largest protection: all commercial use of the product (i.e. not restricted to a specific use) and how the product is processed is irrelevant. Protection of the process claim is for the process and for products that are directly obtainable by the process.
Situation 3 relates to a so-called product-by-process claim. With respect to patentability, the product should be new (inventivity may be obtained through application of the specific process). Scope of protection: in principle absolute product protection, but the danger exists that the courts will deny protection if the product has not been made by the process.