Learn English – What type of sentence is a list of dependent clauses

You can divide this sentence into two separate clauses.

The dependent clause, which provides the reason, is:

To understand the importance of this event

while the independent (statement) clause is:

you should know all the facts

Identifying these two separate clauses, it is then clear that a comma should be introduced between them, by standard rules.

Hence it's most correct to write:

To understand the importance of this event, you should know all the facts.

These are simple sentences. They have a single subject and a single predicate.

In the first sentence the noun clause [ Whatever pizza Lucy orders ] is the subject: and [ is a meal in itself ] is the predicate, in this case a complement.

In the second sentence [ You ] is the subject and [ can choose whatever crust you prefer and size you prefer ] is the predicate, containing the verb and the object noun clause [ whatever crust you prefer and size you prefer ].