Have grammar rules changed through the history of the English language?
When I want to know what form a word has say in 12th century (end Old English, begin Middle English), 14th century (end Middle English), or any other time in England history, I only need to track the word's etymology, and I've got the evolution of said word. But what about the grammar? Should I assume similar rules as the current ones? Is there also any consideration depending of the caste of the person speaking, such as a peasant in comparison to a clergyman or a noble? Is there any interesting reading or online resources on the subject I should know about? (If the scope of the question is too broad, area of interest are 12th century and 14th century.)