Consider the following statements about Bhai Randhir Singh:

1. He was originally named Basant Singh before being baptized into the Khalsa.
2. He was associated with the Ghadar Movement and opposed British rule.
3. He served as the first Jathedar of Akal Takht after Independence.
4. He wrote extensively on Sikh spirituality and mysticism.

Which of the above statements are correct?