We do not usually use all alone to mean 'everybody'. Compare:
All the people stood up. Everybody stood up. (NOT All stood up.)
All can mean everything, but usually only in the structure all + relative clause ( = all (that) . . .). Compare:
All (that) I have is yours (OR Everything ) Everything is yours.(NOT AH-ts yours.) She lost all she owned (OR . . . everything she owned) She lost everything. (HOT She lost all.)
This structure often has a rather negative meaning: 'nothing more' or 'the only thing(s)'.
This is all I've got All I want is a place to sleep. Note the expression That's all ( = 'It's finished').