While I'm learning Microsoft Dynamics CRM 2015, I find out that there is a good built-in software infrastructure available to generate new modules.
Although the features available in the UI are so limited. But working with its SDK, seems it can be used as a tool to create software.
Question1: Is it appropriate to use Dynamics CRM to develop some software unrelated to CRM, for example, Production Planning, Logistics, Warehousing, Accounting, Payroll Systems,....
Question2: How does it compare to other solutions like using DevExpress XAF, Light Switch or solutions like these?
Yes, absolutely, especially with the latest updates to CRM 2015 Online (available On-Prem soon) that allow you to batch updates in database transactions. I have created Student Information solutions, Oil Well management solutions, Real-Estate solutions, Loan management solutions, Donation management systems and several other smaller solutions using the Dynamics CRM framework.
The biggest difference is in how you design solutions. Like any framework, almost anything is possible in CRM but you must design your solutions around the framework features. If you are using a lower-level framework like DevExpress or LightSwitch or even just .NET code, you will have much more power over your user interfaces and code. But with that power comes much more responsibility in maintenance and interface design. Once you get a handle on CRM, you can create almost anything quickly without worrying about the "plumbing." You just have to learn all the different framework features and the associated limitations.