Day trading tax as single member llc

1. Do i need to file quaterly taxes?

if you have taxable income you need to make estimated tax payments

for simplicity I'll merely say 1/4 needs to be deposited  4/15, 6/15, 9/15 and 1/15 of following year

the payment each period can be 1) 25% of your prior year's tax (27.5% if your AGI was over $150k)

or 2) 22.5% of your current year tax   

1) is much easier to know than 2)

2. Am I supposed to pay sef-employment tax (Somewhere I read tradign business is not subjected to self-employment tax).

Normally, you must pay self-employment tax on all income on Schedule C. But in this case, you don't. It's an additional perk of having trader status in the eyes of the IRS. (See Section 1042(a)(3) for more details.)

On the other hand, you don't qualify for a Keogh, a retirement plan that covers self-employed people, and you don't pay into the Social Security system, so you're on your own for retirement.

3. How do I report loss-and-gain from my trading?Sch C or Sch D

without M2M your trading gains and losses go on schedule D/form 8949 and you're subject to the wash sale rules. your trading expenses, not commissions or exchange fees go on schedule c   

Not I have not elected M2M as I need to offset the losses incurred in the previous year when I was not LLC