Reaction of benzene diazonium salts with different compounds

1. $$\ce{ArN2+Cl-}$$ gives addition product with $$\alpha,\beta$$ unsaturated acids, with decarboxylation being integral part of reaction. For example, $$\ce{ArN2+Cl- + Ph-CH=CH-COOH -> Ph-CH=CH-Ar +CO2 + HCl}$$

2. With $$\ce{SnCl2/HCl, ArN2+Cl-}$$ given phenyl hydrazine $$\ce{ArNH-NH2.HCl}$$

I can not find mechanism of any of these reactions, first reaction seems similar to Meerwein reaction (without $$\ce{Cu^2+}$$), but certainly can't follow similar mechanism. Second reaction is completely different from either. What are the reaction mechanisms of each?