Dear student
a) No plasma state does not have a definite shape or definite volume. This is because, it consists of atoms of dissociated gases which have positive and negative charges, which are in their ionised state., without any fixed shape or volume.
b)Plasma state consists of particles which are super energetic and super excited particles in the ionised state, which are in the form of ionised gases. These gases have positive and negative charges which are present in the core of the heavenly bodies like stars, which causes them to glow due to electrostatic interactions between them.
Regards