Hi,
- The missing information are :
- How do you access to your document ? Is it via the other application, via Share, windows explorer ...?
- How do you link the document between Alfresco and the application ? Do you keep the alfresco-id in your application ? Such links imply transactionnal problematics to keep in mind.
- Do you search the documents in Alfresco ? If yes, you should define a custom content model to find them by metadata.
- How do you define your user access on the documents ? Is it handled by Alfresco or the Application ?
- What actions do you need to do on the documents ? (searches, audit, edit, workflow, save metadata ...) ?
Some answers to your questions :
1) When I am designing a content storage in Alfresco , can I use the same file structure as mentioned above or is there better way of defining the document folders in alfresco with different approach ?
Yes you can use the same file structure. But you have to keep in mind how do you plan to use your documents and Alfresco.
For example, a technical structure by date can be good performance wise (you can keep your document/folder ratio < 1000). However it wouldn't be good if your users had to navigate to the document or define access.
3) I work in Insurance industry , is there better way to do define this by making use of any insurance specific Alfrescos feature ?
You can use custom content model to keep insurance information on your document (see bellow)
4) What’s custom content model ? Should I consider this for the above implementation ?
Custom model allows you to keep additionnal information on the document. It can be usefull from a technical and a functional point of view.
Example :
- you can keep the application/process that pushes the document in Alfresco
- if your application generates contracts, you can save the amount, contractorName ... directly on the document
Such information are very usefull for searches, processes, audit ...
https://docs.alfresco.com/5.2/references/dev-extension-points-content-model.html
5) Is CMIS connector supports for retrieving and creating files and folder for the above mentioned structure ?
Yes, but it has some limitations on what you can do and performances.
https://docs.alfresco.com/5.1/pra/1/concepts/opencmis-ext-intro.html
6) Can I use metadata concept for the above structure , how to define a metadata for the above mentioned requirement ? what all the consideration for implementing meta data in Alfresco ?
https://docs.alfresco.com/5.2/references/dev-extension-points-content-model.html
7) Is CMIS connector supports for retrieving and creating files and folder for the above mentioned structure ?
Through Java program (Alfresco behaviour https://docs.alfresco.com/5.1/references/dev-extension-points-behaviors.html or custom upload API)
If you just keep documents in Alfresco without using some capabilities from the product (metadata, searches, access, collaboration, ...), well, a filesystem is just as good 
I hope these answers will help you to define your requirements and your architecture.
