basically , form 4 is your foundation to what you're going to do in form 5.
If you flop in your form 4 , its harder for you to catch up with the syllabus as you will be missing out a lot and will be left behind in the studies.
Honeymoon year? doubt so , many think it is since its after PMR , but from my POV , PMR is just an easy exam. SPM and the college/university exams are the ones that determine your future.

So dont think of playing a fool in your form 4 year. Dont understand anything , just ask your teachers , don't be shy.

Projects and stuff , its simple work actually , ask for a sample of your senior's work from your teacher as a reference. That would ease your burden in the projects.