For your first question: Chinese mobile phone numbers are 11 digit numbers. The fixed phone numbers in Chengdu are 8 numbers.
For your second question:Usually, if your country supports the use of GSM, Chinese mobile phones can be also used there. The GSM has three frequency bands: 900/1800/1900. In China, 900 is more common. Most European or American countries use 1900. So, you'd better take a mobile phone of 1900 to Australia.