The filing requirements are the same for everyone, regardless of age. What makes the filing requirements different is if a person of any age is a dependent of someone else. The 2-year-old that you are asking about is probably someone's dependent. A dependent who has interest income of more than $1,150 (for 2022) is required to file a tax return, whether or not any tax is owed.
If $2,000 of interest is the child's only income for the year, and you are the child's parent, you have the option of including the child's income on your tax return instead of filing a separate tax return for the child. However, in many cases you will end up paying more tax that way than if you file a separate return for the child. The only advantage is that it's a little less paperwork. So the safest course is to file a separate tax return for the child. (If you are not married to the child's other parent, there are special rules for determining which parent can report the child's income on the parent's return. See the IRS Instructions for Form 8814.)
You cannot make a tax payment without filing a tax return. The IRS wouldn't know what the payment is for, so the payment would not be credited properly and they would think you still owe it.
