In the former case we should use periods.

In the latter we should use commas.
4.

A comma is ordinarily used between the clauses of a compound sentence that are connected by a simple conjunction, but a semicolon may be used between clauses connected by conjunctive adverbs.

Compare the following examples: The play was neither edifying nor interesting to him, and he decided to change his plans.
The play was neither edifying nor interesting to him; therefore he decided to change his plans.
5.

To indicate the chapter references in scriptural citations.
Matt.