What type of aldehydes undergo Aldol condensation ?

What structural feature is necessary for an aldehyde to undergo aldol condensation and Cannizzarro' s reaction ? Give the names of the aldehydes which undergo the above reactions.

What type of aldehydes and ketones undergo aldol condensation?

This does NOT undergo aldol condensation :

Assertion : Acetaldehyde undergoes aldol condensation with dil. NaOH. Reason Aldehydes which donot contain a-hydrogen undergo aldol condensation.