I-485 (AOS) approved, travelling on valid AP, when should return

[krupa]

1) Pending I-485 petition (AOS), AP&EAD approved  and valid until another 6 months.
2) I-485 petitioner went to India, on approval of AP
3) While in India, I-485  approved on 29/3/2017 and Card received

Believed that I-485 petitioner can enter on AP when I-485 approved while travelling.
a) Can she enter any time  before AP expires or should return to USA immediately ?
b) Can her spouse carry her GC to India and can she enter on GC instead of using AP ?

Thanks for advice or suggestion