Am I subject to income tax, capital gains tax and dividend tax?

I am 18 years old, I turn 19 in november. I've had a job this year and i've earned approximately $4,000 before witholding tax. Can I get all or any of my federal/state income tax, social security tax, medicare tax or sui/sdi tax back?



Also, I buy and sell stocks. Do I have to pay income tax on any of the stocks I sell that i've held for less then a year? Do I have to pay capital gains tax on stocks that I've held for more then a year? And do I have to pay tax on my dividends?



So basically I'm wondering if there is any exemption for me since I've made only $4,000 pre-tax.