1- I had done the same procedure but I was lucky to find Qatar Embassy in Pakistan. Normally it is required by Labour department to process your work visa but there could be exceptions as they dont ask in all the cases.The requirement is that your degree should be attested from Qatar Embassy located in the country from where your degree is issued, since there is no Qatar Embassy in Australia and vice versa, you need to discuss this thing with your employer.They may have dealt with similar situation before.You can get both original and photocopies attested, just in case you can give them attested copy and keep the original with you.

2- Your salary start from DATE OF JOINING the company.

3- Normally companies provide the ticket but depends upon the company policy, check with them if they will send you the e-ticket prior to your travel.

4- Company should provide the salary during the time your residence permit is processed, make sure they send you the "Business Visit Visa", as you are entitled to work on a Business Visit Visa.