Under what condition would a small UA not have to be registered before it is operated in the U$.$S$?$

When the aircraft weighs less than $\mathrm{.}55$ pounds on takeoff, including everything that is on$-$board or attached to the aircraft.

All small UAS need to be registered regardless of the weight of the aircraft before, during or after the flight.

When the aircraft has a takeoff weight that is more than $\mathrm{.}55$ pounds, but less than $55$ pounds, not including fuel and necessary attachments.