Filing taxes as self-employed for the first time

Hi, I recently quit my job and started a business self-employed. I've set up an LLC and now I'm facing the fun of dealing with taxes directly myself 😉 I have a few questions that I'm struggling to find answers to:

+ I set up the LLC in July, but I don't have any income yet - I've done work but my first invoice will be in September and will get paid in October for work that I've done since I started. I plan to use cash-based accounting. Do I need to file quarterly estimated taxes on 9/15?

+ If I don't have to file on 9/15, are there any implications for expenses? I've had business expenses since I started, do I need to file quarterly estimated taxes in order to deduct those, or can I deduct Q3 expenses in my Q4 estimated taxes, when I actually have received payment for my work?

+ Can TurboTax do the estimated quarterly filing for me? how do I do it?

Thanks in advance for the help,

Rafael