I have a windows server 2008 R2 that has IIS 7.0 web server, Can i install another IIS version 7.5 on the same server? what is the difference between IIS on windows server and IIS on windows 10 local machine?
No, you can not run two IIS Servers on a single Windows Server. And you can not install a different IIS Version on a server that doesn't come with it. BTW, Server 2008 R2 comes with IIS 7.5, not 7.0
The main difference between running IIS on a server compared to a workstation is that a Windows 10 Pro only allows 10 concurrent connections to IIS, while the server version allows unlimited connections. This is the same for Windows 8.x and Windows 7 Pro.
You can install different versions of IIS Express on various Windows OSes, but Express should not be used for production sites.