As per the latest MHT CET Syllabus, there is no negative marking and the difficulty level of the exam will be on par with JEE Main. Students will have to study the syllabus of both class XI and XII just like JEE.
There is absolutely no negative marking. So you can solve the question which you know first and then go for the ones you don't know. So if you are not sure or don't know you can always encircle one of the options since there is no negative marking.