The best copyright would “Copyright © YEAR, Company name”, without any “designed or developed by…”
Make docs for everything you think is important to know. For example, if you use a framework(ex: bootstrap) explain to your buyers how you use it to construct the template, what and how the css/js files are used for, how to edit your template(the right way), etc.
You shouldn’t learn buyers what is HTML or CSS, you should tell them how to edit your item.
Should I grow it the whole month?
No. I focus on CMS not blog platforms. I don’t find it interesting because I like to make experiments and exdend the software as much as I can.(ie. WordPress)
Only primary language is important.
Question: Only one person can win this contest?