IELTS Reading test has several formats unlike other tests that usually come in form of multiple choices. Nevertheless it aims to measure your reading comprehension and the ability to draw important information out from a text. These are skills necessary for studying in English program. Trust me that the papers that you have to read when you really get to study is way harder than this. And they will come in big piles. So my thought is IELTS test is not unpleasant after all.
Formal language means the language we use in serious situation such as school/university essay or paper, job application letter, or published articles. On the contrary, informal language means the language we use with friends and family in everyday situation such as note for friends, e-mail to relatives, or wishing cards. In IELTS, of course, you should use formal words as much as possible. Here are some words that should be noted. More interesting words are in the link.
IELTS band scores explained with examples of weight given to each of the listening, speaking, writing and reading tests.