S5 Active AT&T SM-G870A v5.1.1 OJ3

Just got an S5 Active AT&T SM-G870A v5.1.1 OJ3.

Trying to UNLOCK & IMEI Repair. (Cannot do any w/o ROOT)

Should I DOWNGRADE to NE4 ? Any root for G870A v5.1.1 OJ3 ?

Anyone successfully Unlock & Repair this G870A v5.1.1 OJ3 yet?