Explanation:

About Nankana Sahib

• Nankana Sahib is a city in Pakistan’s Punjab province, where Gurdwara Janam Asthan (also called Nankana Sahib Gurdwara) is located. 
• The shrine is built over the site where Guru Nanak, the founder of Sikhism, was believed to be born in 1469.
• The city was previously known as Talwandi.
• The Janam Asthan shrine was constructed by Maharaja Ranjit Singh, after he visited Nankana Sahib in 1818-19 while returning from the Battle of Multan.

The Shiromani Gurdwara Parbandhak Committee (SGPC) came to existence in November 1920, a month after Sikhs removed partial restrictions on Dalit rights inside Golden Temple in Amritsar.

• It started a gurdwara reform movement which was aimed at taking possession of historical Sikh Gurdwaras, which had turned into personal property of the priests, who were called mahants.
• These mahants were also accused of running practices from gurdwaras which were not approved in Sikhism.
• During British rule, the Gurdwara Janam Asthan was the site of a violent episode when in 1921, over 130 Akali Sikhs were killed after they were attacked by the Mahant of the shrine.
• The passing of the Sikh Gurdwara Act in 1925 ended the Mahant control of Gurdwaras.

Hence only statements 2&3 are correct.