SP2010 workflow or not when jump to any state needed?

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SharePoint2010

Hi, I'm trying to understand if there is a convenient way to use workflow in a particular situation, where:

1- users have to input data at initial state
2- other users have to add other data after step1, based on data previously inserted, but CAN ALSO MODIFY DATA OF STEP 1
3- same situation as step2 but users CAN ALSO MODIFY DATA OF STEP 1 AND 2, so that the step goes back someway
4- other steps like before, some may go in parallel, most of them can jump back to modify data at any previous step, collecting and editing data, and maybe requiring a new review of them

Would adopting workflow modelling help in any way or could only add limitations when implementing the process flow?

Are there any custom development scheme to help in the design and implementation?

Thank you, ciao, mike