APO and SNC in SAP SCM

Dear fiends,

can you please help me on below basic questions

We have SCM system where we have APO already exist and planning to implement SNC as well.

1.we want to understand how the integration and data flow happens between APO and SNC (within SCM) ?

2.what are the benefits of APO and SNC in SCM ?

3.what are the functionalities we can test end to end from APO and SNC ?

4.Do we need PI/PO integration share any data from APO to SNC(within SCM) ?

Thanks,

Satish