Which of the following is/are correct concerning Bharat Stage norms?

1. Bharat stage (BS) emission standards are laid down by the government to regulate the output of air pollutants from the internal combustion engines and spark-ignition engine equipment.

2. The central government has mandated that vehicle makers must manufacture, sell, and register only BS-VI (BS6) vehicles from April 1, 2020.

3. The first emission norms were introduced in India in 1992 for petrol and in 1994 for diesel vehicles.