H1B-less PERM and Two I485s?

请问xiaobaitu和众大虾:
a) If I work with EAD (from spouse's I485), and start an employment-based GC, could PERM and I-140 be approved without an H1B?

b) Could I have two pending I-485s: one as primary, another as dependent? Does the newer one void the previous?

Thank you very much!!!