Size of the Logo and Fonts etc.

Hello Sakin, because of your help, I learned a lot from this free lessons that you are teaching here. I am planning to upgrade to Simple Catch Pro in the near future. But still, be patient to answer some of my questions. 1. What is the size of the logo that I can upload? Because I am using the Theme Logo's function to upload it, but after, I cant see the logo. I was just thinking, maybe it is the size . 2. What are the safe fonts that I can use for the title? because when I am viewing it in my iPhone, it is different from what is displayed in my computer. 3. What are the differences in case that I wanted to upgrade? Can I fully customized it in terms of colors?