how to establish a new department for software development.

Microsoft Team Foundation would be perfect for your needs.

The usual processes for stakeholder requests and change are
1.  Submit Change Request
2. Review Change Request by the Change Control Board (CCB)
3. CCB confirm Approve or Duplicate or Reject
4. Update Change Request if it was rejeceted
5. If Approved, Assigned as appropriate
6. The appropriate team start work on depending on the task involve, it might be a mini project which have have start and end date
7. Verify changes in the Development environment
8. Verify changes in the release build

More tips at
Tips for managing project change requests

I wouldn't say that Microsoft is the end-all, be-all of everything.  And, while you may be using Microsoft technologies for development, there are many things that can affect the tools that are used to manage the software distribution pipeline; e.g. -

What types of technologies are you developing? (thick-client, thin-client, soa, web api, web services, client services, etc.)
What languages are you using? (VB.NET, C#, .NET Core, Typescript, etc.)
Do you want to employ any kind of CI/CD process? (Continuous Integration/Continuous Delivery)
What kind of team workflow strategy do you currently use (or want to use)? (Agile, Waterfall, Kanban)

-saige-

You have no experience in software development, do you?
Asking the question " what are the best tools" is like asking the question "what is the best vehicle".
Microsoft has various software development platforms for building software, depending on what software you want to develop.
Right now, my best advice, based on what info you supplied, is "all of them".

Hi,

Microsoft has following as of my knowledge:

1. TFS (Team Foundation Server)
2. Azure DevOps (formerly called as VSTS (Visual Studio Team Services))
3. You can also use Git for Source Control.

You can manage code and also keep a track of team's work via different dashboards which can also show person wise available bandwidth and work allocation.

CI/CD is what you can also implement which gives more power to your business.

for the Change requests question: Emmanuel's answer can help you :)

Regards,
Pratik

Good morning Mark,

I just want to comment on your post, You a bit harsh on Abu regarding his question, if he knows the answer he will not come here to ask and everyone is free to ask whatever question they want to ask. Asking him "You have no experience in software development, do you?" is not allowed on this forum. The fact that you are expert in your field does not mean that Abu will not become one in days to come. Have a blessed and wonderful day

Regards

Emmanuel

Yes, Emmanuel, you are right, I was a bit harsh and I apologize to Abu.  Answers to questions such as his are not really short and simple cut and dried answers, but are more like discussions on the subject.  AS it_saige pointed out, there are a multitude of things to consider and a multitude of "what do you want to do" questions that need answers.  You could write a book on the subject, and a lot of folks have.

I hope he found a few bits of sage advice and references to explore among the responses.

Hi Mark,

I did really appreciate your humble Spirit.

Kind regards