Does the LED light really help me avoid the quick?

It lights the nail from behind so the pink quick is easier to see, especially on light-colored nails. On dark nails it helps less, so take thin slices and check after each cut.

What battery does it use?

A button cell, LR44 type. It is not rechargeable, so keep a spare on hand and expect the light to dim before it dies.

Is the 10cm mini different from the 15cm version?

They work the same way; the mini is shorter for smaller hands and tighter grips. Both are sized for cats and small pets, not large dogs.

Can I use it on dogs?

Only on small dogs with thin nails. The blades and opening are small, so medium and large dogs need full-size clippers.

How do I change the battery?

The battery sits in the light housing on the handle. Twist or pry open the small compartment, swap the cell with the flat side facing the correct way, and close it.