EWM-2 Step Picking issue

Hi,

I have been doing setup of 2 step picking, currently allocation WT shows destination bin as source bin which is not correct, i have following questions:

1) Is the POSC mandatory for 2 step picking, if do so @ what stage(withdrawal/allocation) system determines the storage process? what are the steps are necessary i.e. OB01/OB02/OB03/0B04?

2) Is the work center  needed during allocation step?

3) How the system determines destination bin during allocation?

4) Can we execute 2 step process without HU/Work Center/POSC?

5) Pls share if there is any doc. which explain complete 2 step picking (apart from SAP Help).

Please let me know.

Thanks,

Ganesan