The Spirus-Belisarus' Diary

In "The Spirus", we are introduced to Soryn and her destiny. Only her tutor knows about the first nineteen years of her life and why everything was kept for her. After the battle at Idric Island, we find her tutor, Belisarus' diary. He wrote about her as she grew, how he taught her to use her gifts, and why he kept everything from her. This is his diary. How did he take her from a locked, guarded room without waking her parents? How did he hide he was Theran from Soryn, given all of her gifts? Why didn't he tell her who he is to her and why, if he knew who she was, didn't he tell her and teach her to use all of the gifts she was supposed to have?