If it's got 5 modes it's almost certainly regulated.

How long does it run for ?

Does it dim or stay bright to the bitter end ?

The light just slowly drops down, it seems like direct drive to me. The 5-modes are just created by PWM I think. I don't even know if it's possible to easily make an 18650 P7 light regulated since a fully charged 18650 will push over 2.8 amps briefly and then less as it drops so a simple boost or buck setup wouldn't work.

2.8A is the most a 18650 can supply ?

No it can supply more, but the Vf needed to push over 2.8A is too high for an 18650 except when fully charged.

Wouldn't that only apply to direct drive ?

If you had a 2800 mAh driver it would pull more amps as the voltage decreased ?

2800mA you mean but yes it should. When I get home I'll measure Vf across the LED as the battery drops down and see if it changes. If Vf holds steady, it is indeed regulated. But I suspect it isn't because when I experimented with some thinner gauge wire, the minor voltage drop across that wire had a visible effect on the brightness of the light which shouldn't happen.