The correct option is option 4. It is not correct to say that India has the largest railway network in the world. Based on the latest data, the countries with the largest railway networks are the United States, China, and Russia.

Let`s examine the other options for a better understanding. Option 1 states that the Indian rail networks have been developed throughout the Konkan coast. This statement is correct. The Konkan Railway, a subsidiary of the Indian Railways, was established to develop railways along the Konkan coast, connecting Maharashtra, Goa, and Karnataka.

Option 2 mentions that there is very low density of railway lines in the Himalayan region. This statement is also correct. The difficult terrain and challenging geographical features make it challenging to build railway lines in the Himalayan region, resulting in a relatively low density of railway lines.

Option 3 states that the north Indian plain has a dense network of railway. This statement is correct. The north Indian plain, which includes states like Uttar Pradesh, Bihar, and Punjab, has a well-developed and dense network of railway lines, facilitating the movement of people and goods.

In conclusion, option 4 is not correct, as India does not have the largest railway network in the world.