I know that it's recommended to put all the qlikview documents on the qlikview server and my question is:
The different database (mysql, oracle, excel ... ) to which we connect the application during development should also be on the server so that if we change the level of the database application take into account?
Not sure what you mean by "change the level of the database application". Please remember the QlikView server uses a lot of memory and has a working set this it setup with the server when it starts. SQL and Oracle does the same think and this will cause performance issues with the server. QlikView only needs ODBC connections to the SQL Or Oracle servers. The data is only read into QlikView when a document is reloaded.
If I understand you correctly if the data in the SQL database changes how do you update the Qlikview Dashboard. You would have to do a reload. If you setup the ODBC connection to match what you are using on the developemnt machine then the QVS can do the reload for you.