2. What inputs are used for hashing? I've read about Nonce, timestamp, extra Nonce.
Block header, which have 80 bytes size. Aside from 3 field you mentioned, IIRC overt ASICBoost also manipulate nVersion.
6. Why hash rate keeps fluctuating? E.g. for my LV07, it averages 1.0TH, but fluctuates between 0.85TH - 1.2TH. Every 3-4 min or so it reaches low point, and in the next 3-4 min it reaches the high point. And on, and on.
Without additional information, i would speculate your LV07 is in loop due to overheating where it underclock itself temporarily.