Yes, you'll need to report this 1099-K on your tax return. While the 1099-K issuer must provide a 1099-K if the reportable payments are $5,000 or more, they may provide a 1099-K with any amount on it. Not receiving a 1099-K because the amount received was under the reporting threshold does not excuse individuals from reporting taxable income.
Here's some information you may find helpful: What is Form 1099-K?
Yes, all income from all sources is to be entered on a tax return.
Go to this IRS website for what you are referring to - https://www.irs.gov/businesses/understanding-your-form-1099-k#threshold
Third party settlement organizations (TPSOs) – which means (payment apps and online marketplaces – are required to report payments on Form 1099-K when the total amount of payments you receive for goods or services through the platform exceeds:
Although the reporting threshold is phased, you may receive a Form 1099-K even when total payments are less than the reporting threshold. No matter the amount of reported payments, if you receive payments for selling goods or services, you must report all income on your tax return.