The correct answer is option 3 - Both 1 and 2.

Option 1 states that a major difference between a written and an unwritten constitution is that a written constitution is the formal source of all constitutional laws in the country, while the unwritten constitution is not the formal source. This means that in countries with a written constitution, all laws must conform to the provisions laid out in the written constitution. On the other hand, in countries with an unwritten constitution, constitutional laws may be derived from various sources such as statutes, court decisions, and conventions.

Option 2 states that a major difference between a written and an unwritten constitution is that a written constitution is entirely codified, while an unwritten constitution is not. A codified constitution is one that is written down in a single document or a series of documents. It provides a clear and comprehensive set of rules and principles. In contrast, an unwritten constitution does not have a single written document but is based on a combination of laws, conventions, customs, and historical precedents.

Therefore, both options provide accurate major differences between a written and an unwritten constitution.