Explanation:

1 and 2 only

As early as 400 BC, Indians learned how to manipulate iron in ways that we don’t fully know even today!

The Iron Pillar that refuses to rust
The iron pillar near the Qutb Minar in Delhi is a perfect example of the genius of ancient Indians. From the Gupta era in the 4th century AD, this iron pillar has not rusted in over 1,600 years. Scientists spent decades puzzling over how this was possible. After many tests over many years, they realised that the pillar’s iron has an unusually high level of phosphorous, which reacts with moisture and creates a thin protective coating of hydrogen phosphate hydrate on the pillar’s surface to prevent rusting. So the rain and wind, which would normally cause corrosion, actually helps protect the pillar!

Inventors of steel
Indians also produced the first true steel, fusing iron with a high amount of carbon (1 to 1.6 per cent). They did this by sealing iron and charcoal into clay containers called crucibles, and roasting these at extremely high temperatures in furnaces. When they broke open the cooled clay containers, pure steel ingots lay waiting for them, with even amounts of carbon throughout the steel. This steel was extremely tough, shatter-resistant and able to be honed to the sharpest edge.