Broken home buton
As shown on your video
Don't remove the front screen screws that have washers, only loosen them and it will save you time and hassle when re-assembling the phone.
Buy the IFix it 000 screw driver and a magnifiyng galss on a stand or head holder for this job.
P2 Pentalobe Screwdriver iPhone
iPhone 4 and 4S Speaker Enclosure
iPhone 4 Home Button Assembly