Explanation:
According toaccording to your first question that you said and in your opinion which make this literature so difficult to read is it the vocabulary the characters the type of trying the density of the language it is because of the density of the lanuage, because the language they use then is quite denser and different from the one we are using today. as you know as we move on from generation to generation, things are being simplified due to the development of technology and the rest.
And also your second question looks similar to the first one. As you read from Old english, tou find some words strange and even quite logical, difficult to pronounce, e.g this word, thou, this is due to the time and era in which the've lived, thats the kind of languages and assents they use.But as you move to Middle english, oh, now things are starting to get simpler, you see, it goes like that, you can understand some words, but some looks trivial.It goes like that, things changing gradually,as you move, until you get to the Modern english, where everything is fully clear.So this changes are as a result of the time, generation and era in which different catefiries of people have lived,are living and will live in the future.
I hope you will find this really helpful.