Yes, feathering locks engage at 800 RPM on the Seneca.
We feather to stop windmilling and reduce drag.
No, you mechanically change a valve that changes the air intake to air that runs past the exhaust manifold and is therefore heated.
17KTS
No, it’s not required as the Seneca has a fuel injection system and engine icing normally forms around the venturi of the carb.
Ice can still form in in a fuel injection system in icing conditions, an alternate air source is available in this situation which takes warm air from inside the engine cowling.
Only hydraulic gear.
Seneca uses MOGAS (red) or AVGAS (Blue)
Alternate air is an alternate source of air, it can for example be used during ice, when the normal filter is blocked to have a backup source available.
Alternate air is unfiltered air and should not be used during ground operation because the unfiltered air may contain dust and other contamination.
Only hydraulic gear.
The engine will flood with fuel.