In Direct objects^x, Commas^x

As the direct object of the verb, the list requires no special punctuation; I choose the last of the three.

I wouldn't know how to give a detailed explanation or description of all three types of clause in one post, so let's go step by step. Let's start with adjectival (or relative) clauses, since these are the easiest to identify. They can function only as postmodifiers of a nominal head. This...

You should not use colons here because the clauses coming before the colons are incomplete. As far as I know, the verb coming before a colon must have a direct object. Commas are correct in both your sentences.