Custom list approval workflow using Sharepoint 2010

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SharePoint2010

I got multiple departments.

I created a list where all the departments can save their data and they may see the vacant stuff to utilize across different departments, however they need to get the ownership change from that department A to the department B who wants to use that stuff, for that i want Department A to send a request for Approval and get it approved from department B to use that stuff...

My questions are:-

1 Do i need to create a separate custom request list or i can add workflow to the list where all departments are uploading data

2 When department A raising a request and that goes to selected department who has stuffs vacant, how would he approve back to that request, do i need to create a separate approval form or can add columns in workflow to add a separate approval form.

3 After creating a workflow, how would i associate that with my Custom list or library

4 If possible please help to get the calculation done in that particular workflow to populate monthly reports.

Please help me....!!

Thank you.
Sharepoint learner