Never even realised this was an Australian thing. I kind of assumed it was a universal English thing, with the more Australian variant being "no wuckas".
'No wuckas' is nowhere near as common as 'no worries' in Australia. 'No wuckas' is only when you're being blokey and making a point of the phrase; raising the 'ocker' factor. Most day to day usage is 'no worries' - in most retail shops, for example, if you thank the staff for help, they're not going to say the 'wuckas' variant.
Absolutely, it's a much less formal term, primarily due to the origin.
No wuckas? Now you're just making stuff up.
Nope, very Australian, with another varient being "no f$&king wucks"
No they're not. It's short for 'No wucken furries', but it's used in a more humorous way and not in polite company.
Nope, that's often used. I personally don't use it, but I know others who have, frequently.