Party Formation: It was founded by A.0. Hume in 1895 with the intention of gathering educated Indians who can convince Britishers and their policies in favor of India and gain freedom later because of the continuous failures in the agreement of policies made by the Indian scholars. At that time, Motilal Nehru was the founding member of the Congress.
 

What happened in the time of pre-Independence?
Nehru, a party member of Congress who participated in several freedom movements along with Gandhi, made his position strong in front of Gandhi. Even though much more potential and group-favored leaders are there, like Sardar Vallabh Bhai Patel, Rajendra Prasad, and many more.
And the main mistake is it's failed policies For the protection of people of both the countries of India and Pakistan due to it's political rivalry between the Muslim League and Congress. In fact, it is the personal rivalry between the leaders of the parties. 
The lack of implementation policies in an economical way disrupted India's power more than imagination. 
Loans lent by Prime Minister Nehru from Britain made an agreement that time saying to reduce the value of the rupee in return for its amonut received from India, and that money was used to give Pakistan to compensate for partition. Issues with Pakistan. 
 

Foreign Policies:
Gifting a part of Indian territory to another neighboring country is not a single person's decision or a parliament to take; there are provisions for bordering alterations and name changes and a few limited works associated with the land of Indian territory, even though it is an island part of India. Katchatheevu, which is given to Sri Lanka to improve bilateral relations, led to a war between Tamil Nadu and Sri Lanka, which was an important part of fishing, an ecosystem, and a key temple on the island.
 

Bordering conflicts
There are disputes in the region of India and Pakistan, especially in the region of Kashmir. When Kashmir was added to the Indian territory with Article 370, there were few problems associated with it, which led to abuse of the culture of the local people. If the serious measures were taken at that time only, there would be fewer problems associated right now. At present the condition is deteriorating as POK gave some part to China, making it a three-country issue where China always wanted to occupy the land, which is in lack of observation or to claim. 
 

Defence :
Lack of transparency in the defense sector, in the time of Rajiv Gandhi, in the mean time of signing contacts for defense technology during their operational time is well known for most of the people as the Bofors scam. And in the usage of the army in different war periods, there is also a controversy to discuss.
 

Fault in leaders, lack of transparency, and lack of technology at that time, and a newly born country will definitely have its own problems. It needs a strong leader to carry out the vision and goal of India, not in the name of the party. The above-given points are the faults in policies, but there are certain policies that are not considered here.