Alkyl Halides give cyanides with KCN but isocyanides with AgCN as the products. Why ?

Alkyl halides react with KCN to give as the major product

How do the product differ when ethyl bromide reacts separately with KCN and AgCN ? Name the products.

How do cyanides and isocyanides differ in their structure ?

Reaction of an alkyl halide with KCN and AgCN gives different products ? Explain.

When alkyl halides are treated with Ag_2O they give

Haloalkanes react with potassium cyanide (KCN) to give alkyl cyanide, but gives alkyl isocyanide with silver cyanide (Ag CN).

Alkyl halides though polar, are immiscible with water, why ?