Wikipedia:Simple talk/Archive 98 Complete, exhaustive vocabulary list
No, but you don't have to use only the words listed. First, all versions of a noun or adjective are included in the main word listed. Verbs are a bit trickier, but the infinitive plus basic tenses are included. Second, you can go outside Basic English, but take care to explain or 'translate' words readers might find difficult. There is a list of Most common words in English, and you should regard any word in the top 1,000 as being simple. Research has established that the more common a word is, the better it is understood.