Quote: "1. Make my voice deeper? Since i'm only 12, my voice isn't all that deep."
It's very hard i think to make it sound real, but you could try messing with the pitch controls and sliders inside the Flstudio sampler. Maybe add an eq and increase the lower frequencies to get a little bass in there.
Quote: "2. Are there any other programs that allow me to make voice files, other than "Sound Recorder"?"
You could use Flstudio to do that, i believe there is a video tutorial on how to record audio in fl on the flstudio webpage. Or you could download and use audacity wich is a free audio recording/editing program.
Quote: "1. Is there any way to easily understand Styrus? The videos are really confusing for me."
It's all about learning how to use your synth, there is no easy and fast way, or a quick route on how to learn to use it. If you keep at it making your own presets and playing around with it then you'll eventually get better and better. Personally i wouldn't spend money on sytrus, i've been using the 3xOsc wich is an amazing synth that can produce quality results that are equal in quality as something sytrus makes. And it comes for free with flstudio.
I hope that answers your questions a little, if you've ever got more questions on how to use fl, feel free to ask here and i'll try to help you
Have fun playing around with fl!