The load path runs symmetrically up both uprights, so the frame is in balanced tension rather than trying to open like a C. It deflects far less under load, which means force is applied where it is aimed and accuracy holds up at rated capacity.

It sits on pins passing through both uprights and is moved up or down to suit the workpiece, setting the daylight available. The number of pin positions and how easily the bed can be repositioned determine how usable the press is in practice - more than the tonnage does.

Throat width between the uprights, and the fact that long workpieces cannot pass through the frame. Anything longer than the working area or awkwardly shaped may simply not fit, which is the case a C-frame or roll-frame exists to cover.

Generally yes, because the work is enclosed between the uprights rather than sitting on an open shelf, so a component that releases suddenly is more likely to be contained. That does not remove the need for a guard, which remains the primary control against ejected fragments.

Enough for the heaviest routine job with margin - bearing and bush work needs relatively little, while straightening and heavy interference fits need considerably more. A press used at its limit on every job is undersized, and the next size up is usually a modest price difference.

Hand for occasional use and fine control; air-over-hydraulic where compressed air is available and work is repetitive; electric for production or large capacities. On a big press the number of hand strokes to reach working pressure is what makes people wish they had specified otherwise.

Yes - off-centre loading puts a bending moment into the ram and the frame, and it is a common cause of bent rams and damaged beds. Many H-frames allow the ram to slide across the top beam for exactly that reason, and using that adjustment properly matters.