Work experience query

Hi,
Can anyone please answer these queries regarding work experience for australian immigration.

1. Can we use part-time experience as a part of 4 year work experience requirement ? i.e 2 years part-time equivalent to 1 year full-time . Or do we need to have full-time experience only.

2. Can we show pre-study work experience ?

3. Is it possible to show full time work and full time study at same time ?

4. Is it possible to show full time work while on student visa in UK ?