If I received a 1099-NEC for $400, do i need to file a schedule C (Long tax form)? I am a college student and only reported $2,000 in total income in 2024.

If it was self-employment, you are starting a business and trying to make a living, then it is reportable business income. If it was a one off and you happened to make some money, it is not self-employment and you are below the threshold.

 Let's take a look at  Earning side income: Is it a hobby or a business? which lists 9 factors after stating that a hobby is for recreation, not for profit:

• Whether the activity is carried out in a businesslike manner and the taxpayer maintains complete and accurate books and records.
• Whether the time and effort the taxpayer puts into the activity show they intend to make it profitable.
• Whether they depend on income from the activity for their livelihood.
• Whether any losses are due to circumstances beyond the taxpayer's control or are normal for the startup phase of their type of business.
• Whether they change methods of operation to improve profitability.
• Whether the taxpayer and their advisors have the knowledge needed to carry out the activity as a successful business.
• Whether the taxpayer was successful in making a profit in similar activities in the past.
• Whether the activity makes a profit in some years and how much profit it makes.
• Whether the taxpayers can expect to make a future profit from the appreciation of the assets used in the activity.