It isn't necessary to take any action for a completed song to be protected. Copyright protection is automatic, as soon as work of sufficient originality is "fixed in a tangible medium, perceptible to human eye, machine reader or other device".
If you want the additional protection a formally registered copyright can provide, contact the copyright office in your country for the proper procedure.
The work must include the following
The only really legal requirement for a work to be copyrighted is that it hasn't been done before. Basically it must be your work and no one elses. If you meet that requirement you may copyright it, but copyrighting requires a down payment of money including federal and state taxes. Copyrighting something ranges from around $100-$300 depending on your local state taxes on copyrighting a ideal.
Because protection is automatic, a notification is not required: everything is protected by copyright unless it specifically says otherwise.
That would be copyright infringement if the original song was protected.
Because notification is not required for protection, it is safe to assume that any mp3 is protected by copyright unless explicitly stated otherwise.
The song will be protected through 2050; recordings will be protected longer.
No; it is a traditional Jamaican folk song.
There are many works by that title, but the song by Alice is protected, and recordings of the song are additionally protected: one copyright on the underlying tune, and one copyright on the recorded performance of that tune.
Short phrases such as song titles cannot be protected by copyright.
Short phrases like song titles cannot be protected by copyright.
Yes; it was written in 1961 and renewed, so it will be protected through 2056.
Yes; it is controlled by EMI Feist, and will be protected through 2034.
No, but a new work based on a PD song can be protected by copyright. A new translation, setting, arrangement, etc may be copyrightable. A common example would be the traditional Shaker song "Simple Gifts," which is in the public domain, and Aaron Copland's popular orchestral setting "Variations on a Shaker Melody," which is protected by copyright.
Both the song and all recordings of it are still protected.