At my armored job, we had a barrel half filled with sand that we had to point our weapons into in order to decock our guns.
Second question depends on the gun and the holster. I always carried my gun chamber loaded, hammer down, safety on. Since most people had DA only guns, it wasn’t an issue for them, but I don’t recall ANY of the non-DA or revolver people carrying with hammer cocked.
I don’t carry or anything, so don’t know if my $0.02 is worth $0.005.
1 is normally used for single action like the 1911. The idea is that it is ready, but safe.
2 may be ok for SA or it may be not. If it’s old, etc. If you can’t put the safety on when the hammer is down like some firearms, then you are old relying on the DA trigger pull, which reduces the risk of accidental discharge but does not eliminate it.
Revolver obviously not C1, because you can’t do the locking part.
The explanation I’ve been given is that IF you let the hammer slip and the gun discharges, not only has your gun gone off unexpectedly, but your thumb is now occupying the same space that the metal slide of the gun will be filling momentarily.
Remember: You are made of squishy bleedy bits, while your gun is made of solid and often sharp metal bits, and that slide is moving FAST. I’ve never had it happen, but the instructor at the shooting range last week had seen it on the range before, and he told me that it looked pretty painful.
As far as how you carry it, as others have said, it depends on the gun. Aside from different trigger mechanisms, some weapons have various built-in safeties (the Beretta 92, for instance, has a piece that rotates when you squeeze the trigger. Don’t squeeze the trigger, and this piece will block the hammer from hitting the firing pin. Note that you cannot manually decock a Beretta 92 without squeezing the trigger, and we come back to the top paragraph.
But yeah, with the Beretta, we were told to carry it loaded, chambered, hammer down, safety off, unless ordered otherwise. Don’t put your finger on the trigger until it’s pointed towards the bad guy (or paper targets or whatever), and it shouldn’t go off that way.
If it’s a DA/SA firearm it should have a decocker, which will drop the hammer with no risk of discharge (assuming proper function). If it’s a 1911, what’s the benefit of lowering the hammer on a live round? If you’re going to make it so that you have to draw back the hammer anyway before firing, don’t even bother. Just rack the slide.
For the record, I carry my 1911 cocked and locked. There is no possibility of the weapon firing with the safety on, and you determine the condition of the safety the moment you flick it on. If it’s loose or won’t stay, the firearm is broken and shouldn’t be used anyway.