The "25-50" rule is only applicable to CSP students.
For both local full fee paying and international students, they will be sent to rural areas during their 4-year studies for 6-10 weeks in every term.
...for a single term, not every term. A term (rotation) is 8 weeks at UQ for example, but 2 of those weeks during the rural term is doing orientation and projects in a regional centre, leaving 6 weeks actually rural.
There is no rural working during internship period, right?
I think there are some exceptions where interns do go; as I recall the intern contract has the same stipulation. In practice though, it's by far chiefly JHOs. The hospitals I know about also wouldn't make you go each year - time served is recognised.
After internship, 10-15% of them will work in rural areas for 4-10 weeks during their contract. What is the length of period of their whole contract usually?
It's a 1-3 year contract for junior docs (in Qld at least), depending on level (for me was 1 year as intern, 1 year as JHO, then 3 years as SHO). Each time it's re-"negotiated" at which time you can elect to go somewhere else (or give notice and go earlier, assuming you have completed internship, unless you're in NSW I believe since your first contract is for two years? - someone correct me if I'm wrong). If at that time you stay put in the same hospital, it's normally rubber-stamped, i.e., you don't have to sweat out whether or not you'll have a job for the next year.
Fr the rest of graduates, they are 'lucky' enough that they probably can stay in cities.
I wouldn't think of it as staying or not staying, since you're put up in Qld Health housing while on secondment to a rural locale. I've lived in Brisbane for 6 years and gone rural as a doc twice (by choice).
Does the junior house officer have full practising licence?
Not sure what you mean here. "Full registration" is conferred after internship, but that doesn't have much practical significance, except it's easier to move inter-state once you're fully registered.
You can't practice independently until you're specialized. However, if you have permanent residency, you can do locum work at hospitals after your JHO year and make significantly (3 to 4 times) more than as a hospital house officer.
By and large, specialty training doesn't start until after the JHO (RMO1) year. The main exception is GP training, but the first year there is in a hospital as a house officer, so assume two years out (or more) doing 5 terms per year, then you can join a specialty college, then 2 to 6+ years specialty training, then you're a consultant/fellow.
Between JHO and specialty, many elect to stay in the hospitals as a Senior House Officer (doing additional terms in whatever fields), or as a Principal House Officer (doing specialized training in a particular field, but as a house officer and not counting as part of a college's specialty training requirements).