Consider the following statements regarding the Punjabi language:

1. Punjabi is an Indo-Aryan language spoken by over 100 million people worldwide.
2. It was introduced as an official language in Punjab on 13 April 1968 under the Punjab Official Language Act, 1967.
3. The Gurmukhi script is used for writing Punjabi in both India and Pakistan.
4. Eastern Punjabi, spoken in India, has four major sub-dialects: Malvai, Majhi, Doabi, and Paudhi.

Which of the above statements are correct?