It is HIGHLY recommended that you check with your local authority to ask the question directly. Each municipality has the right to decide what they require to be permitted. They will also inform you about any requirements for your contractor if needed, such as state or city licensing.
Depends If its a load bearing wall then you need a permit and most likly a structral engineer to look at it also which in turns leads to having a blueprint done up before the permit process is started.
This question is highly state and town dependant. Depending on the state, county, or town you are located in would answer this question. Mostly likely yes, however there are places where such work would not need a permit.
For items 1 and 3 you definately need permit. For item 2 you do not. Basically for any new addition you would need a building permit. If you are in Los Angeles area we can provide you with free estimate.
Each state is different, but yes, in California definitely, you’ll also want the permit since it will record your changes to the house, for example adding another room, which can add more value to your house.