1. Is project charter ever changed across the course a project phase or a project life cycle ?

minor amendments/addendents/ alterations may be so that objective/SOW could not be affected.

2. If it changes does it go through the Integrated change control process ?. Is there versioning for Project charter !

No only issuer can change if so. there is no version but PC of phases may be created on master PC of project charter.

3. Who will sign the charter for any changes made on top of it ?

only issuer can change if so.

4. If a project charter changes, does that signal  that the current project needs to be scraped [extinction] ?

project charter never be a cause ------------, it is a cause that a project is valid to start and run

5. If the scope of the project is changed/modified as part of a customer request, how it will get reflected in Project charter and the measurable objectives in that ?

within the objective /SOW 

6. Is project charter a legal agreement ?

PC is internal document - it is down the line - may be a document of authorization/order. Buyers PC may be a basis of agreement details BETWEEN seller/buyer

7. The project has comlpeted planning phase and into execution. But the new PM realizes there is not project charter created /available. Should PM try to get the project charter newly created at this stage ?

not must, but it may be

regards