the advantage of taking your benefits before full retirement age is that you collect benefits for a longer period of time, the disadvantage is that your benefit is reduced.
Is there a way that I can know what would be the reduced amount I'd receive if I retire early?
yes, there's a chart that lists age 62 reduction amounts and includes examples based on an estimated monthly benefit of 1000$. You can select your age on the chart to see how much your benefit will be reduced if you retire before full retirement age.
What's the earliest age I can start receiving retirement benefits?