1. Install the EMDK for C and the PSDK for MC2100
Go through the EMDK release notes for other requirements, but the above should be most of it. I don't think you actually need the CE SDK if you load the PSDK.
By the way, if you have not done WINDOWS Programming in C/C++, you might find using .Net easier.
2. Some MC2100s come with the core OS and some with Professional, so depending on which you order, install the PSDK that matches. You can use Visual Studio 2008 and the EMDK on Windows 10 (probably not officially supported, but people have made it work), but there are some things that are not ideal. One typical issue is that the shortcuts to the sample apps and help file are not obvious. Look in C:\Users\Public\Motorola EMDK for C\v2.8\Samples and C:\Program Files (x86)\Motorola EMDK for C\v2.8 for the help file.
3. Windows Mobile Device Center 6.1 will work on Windows 10 (probably also not officially supported though). This is what you will need.
4. Once you have a device, you should be able to request the download from support using the serial number of the device (since it will be under warranty). Any restricted downloads will only be available to you if you have a support contract on the device, or if the device is under warranty.
Also, pasting in the below from the EMDK for .Net release notes. I think this also applies to C/C++ even though it is not called out in the notes:
The edition of Visual Studio installed must support mobile device development. Express editions of Visual Studio do not support mobile device development. Visual Studio 2008 Standard Edition does not support mobile device development.