1. I find comfort bikes are often lumped in with hybrids, but hybrids won't neccesarily have suspension/seat shock absorber/tiltable bars, etc... my Devinci St-Tropez hybrid has no comfort features, but they make a comfort model with the same frame.
2. SOME bikers can run a MTB with slicks as fast as a hybrid. Then again, some can use 2.5" offroad tires to go as fast as a race bike if you believe their claims. I find I'm going WAY faster on my hybrid than my old MTB, but then again, it was *ahem* a 1987 Sears "Free Spirit" and probably outclassed by anything that's considered a bike on this forum.
Hybrids vary, but I'd imagine you'll find something between MTB and road gearing. Also, aside from raw sizes of gears, hybrids often have larger tires. Mine are 29". (I often brush my feet with the front tire when doing sharp corrective steering on narrow paths, but that's good-- the pedals should be under the balls of my feet, not the arches!)
3. Can't say, it probably varies a lot. Like I said, mine's not a COMFORT hybrid, so it feels like a smooth, fast MTB. Definitely the right one for road/commuting with shortcuts though. It even holds its own on dirt trails if the hills aren't too steep for my semi-slick narrowish tires.