Are 100 speeds really different from each other?

The control is stepless, so the fan moves gradually through its range rather than jumping between a few fixed levels. The practical benefit is a very low, quiet setting for close use; the top end is still limited by the fan's small size.

How long does the battery last?

Runtime depends heavily on the speed you choose. Expect the longest run at the lowest settings and a much shorter run near the top of the range. Charge it over USB from a laptop, wall charger or power bank.

Can it run while plugged into USB?

It is USB powered and rechargeable, so it can run from a USB source while charging. That makes it usable at a desk for long stretches without draining the battery first.

Is it quiet enough for a bedroom or office?

At low speeds a small fan like this is quiet enough for a desk or nightstand. Noise rises with speed, so the higher settings are better suited to daytime use than sleep.

Does it oscillate or come with a remote?

The listed functions cover USB power and rechargeable operation only. No oscillation or remote is stated, so treat it as a fixed-direction personal fan.