Do you need to put these back on after you remove them?

Do you need to put the screw covers back on after replacing the fan or is it ok if you forgot to put them on ? Sorry for the basic question I just want to make sure .

After you remove the adhesive from the battery. I am assuming upon reassembly that it will not have adhesive to stick to the case. is that ok? or will the battery move around due to that?

sorry for the basic question, i just want to make sure i know what to expect upon reassembly.