The first two questions are the same. So I explain one of them. 先生请念这页！= 先生请念这页了！The two sentences are not the same, the first 先生请念这页 means this page are not finish. 先生请念这页了means this page have been finished now, should change to another page. As my English is not so good, I don't know if you can understand me. 2_what kind of are true?先生=Xiānshēng or 先生=Xiānsheng?? Xiānsheng is right.