Wolf-Kishner reduction: Reduction of carbonyl into alkane with hydrazine in high boiling solvent such as glycol .

This reaction is not preferred when base sensitive groups like halogens  or bulky groups are present.

Clemmensen reduction: reduction of an aldehyde or a ketones with zinc amalagam and concentrate Hydrochloric (HCl) acid.

Note; Clemmensen reduction not  suitable for those compound having acid sensitive groups ( basic in nature) such as  Alcohol, amines, alkenes, ester, cyclic ketal, nitro etc.

In The Cannizzaro, The intermediate That will be The best hydride donor is:

Ans (3) Dioxide anion is a better hydride doner, and presene of -OCH3, group further increases the electron density.

Note: Dioxide anion form in cannnizzaro reaction when concentration of Base  taken high  and the reaction becomes 4rth order reaction.