Install new SAP system from Backup File

Hi,

We have an requirement to install new SAP test system for PI.

Here I have few Question.

1. What are the steps we require to Install new SAP system from Backup File?

2. Can we use online backup file?

3. Do I need to restore backup after installing database or I can choose backup file from SWPM , while installation?

4. If I use export\Import method , does export of system require downtime ?

Please Suggest.

Thanks and Regards

Amit