SAP ERP6 TABLES and S/4 HANA

In S/4 HANA system ; Does anybody know for certain that if you had a old ABAP report program that was reading MKPF/MSEG or MBEW and MARD-LABST

1. would it actually read data from the S/4 tables ?.

2. If you needed to write a new ABAP program how best to access the data? e.g. Can you still write ABAP SELECT on MKPF or should you SELECT on MATDOC.