Yes, in the long run. The 220 volt unit will use less power.
no.
Only use 110-120 volt appliances on a 110 volt socket.
Typically they are either 220V or 110 volts not both. Plugging a 11o volt blanket to a 220 volt line has a huge risk of fire.
NO
Yes
no
Yes - usually house voltage varies from 110 to 120 volts.
115 Volt and a 110 Volt can be treated as the same thing. The electrical voltage supplied from your electric company is not exact and can be 120 Volt + or - 10%.
No adapter is needed, 110 and 115 volt are interchangeable.
No, the applied 110 volt is too high for a 3 volt appliance. The appliance would burn out right away.
Yes.
Yes.