Hi Auravella, I believe you've written to our helpdesk earlier - we've replied to your requests just now, so kindly check your email.
Just to answer your questions, please see below:
1. Here's an article with basic information on how you can create your own lessons (the instructions apply even if you are not trying to translate the existing English lessons):
http://support.brillkids.com/entries/20622132-How-can-I-translate-my-Little-Reader-English-Curriculum-into-the-language-I-want-to-teach-2. By default, Little Reader will "take care" of rotating the words as well as all recordings, pictures or videos included in each word. You don't have to choose which specific word, picture, etc. will be shown for each day. However, you will still have an option to set specific playback settings.
Unless you specifically edit your premade lessons to add or remove words or any media file, or if you deliberately remove some categories from your course, your newly-made content won't replace the existing lessons.