Before talking to the statue: 1. Be sure that you read the "Book of Nemris". 2. Be sure that the book is in your inventory. 3. You have one shot to gain the benefit from statue's test. You must reply its questions correctly. All answers are in book.
About frogs: You will see four frogs in the lake at the center of Nericon's Garden. Kill them all and a portal to the north of lake will be open. Go through to reach a secret treasure room.