cross dependency between SAP BW 3.5 and BW 7

Hello Experts,

1) Can you please explain cross dependency in between SAP BW 3.5 and SAP BW 7 for Query designer, Bex Analyzer , Workbooks and web templates ?

2) can we make copy of query in SAP BW 3.5 version and keep it SAP BW 3.5 Version and original query upgrade to BW 7 ? what we need to do ?

3) can we upgrade queries to BW 7 version and can still use Workbooks in BW 3.5 version ??

Please advice.Thanks in advance.