Hi
I first came to US in 2009 with an immigrant visa but had to leave without my green card and were out of US for more than 2years.
I finally came back to US with a returning visa (SB1) in 2012, and they gave me a green card which its date shows 2009. Am I eligible to apply for citizenship ?

To be naturalized, you need to have "continuous residence" in the U.S. for the last 5 years (or 3 years of "continuous presence" if you were married to a U.S. citizen for the last 3 years). "Continuous residence" is generally broken by an absence of at least 6 months, and definitely broken by an absence of at least 1 year. So you broke your continuous residence when you went away. Under the 4 year + 1 day rule, if you broke continuous residence with an absence of at least 1 year, you can apply for naturalization 4 years + 1 day after coming back from that long trip (or 2 years + 1 day if you qualify under the 3 year rule).