Can the existing tools, web systems, CRM, etc. can be connected to the new application?

In most cases, yes. If the company has API documentation, the developer might be able to integrate it with the system.

How is the data-sharing handled between the mobile and web platforms?

A central database is created that will be holding all the data. Then an interface or API is placed that allows the mobile and web apps to send and receive the data. While building a connection between the mobile and