Basically the behaviour of a complete loose cunt, someone who does what they want with no thought of later consequences

Crazy. Has mental issues. Can relate to someone who has done too many drugs.

Heading "out the gate," or literally through the wire, and entering hostile territory while on a combat patrol, such as in Afghanistan or Iraq. "Out the gate" is also the terrain which is beyond the fencelines / walls of your compound.

since you were born, since you came out of the womb

Kiwi term describing someone who is on drugs, probably a private school rebelling against their parents.

To do something for no apparent reason or with no provocation.

It means to get out of jail.