It’s impossible to get a 1.1 only API using any thing at all to do with vertex buffers, because vertex buffers did not exist at all in 1.1.
If you want to use a 1.1 API then the simple solution is to just use 1.1.
If you want to use GL 4.x on Windows, then you absolutely can. Wherever you sourced the information from that Windows only supports 2.1 is a load of old nonsense.
The primary factor that determines which GL version is supported is hardware. Not software, not OS.
Hardware functionality is then provided by the GPU vendor’s device driver. OS is only relevant in that the GPU vendor must make a device driver for the OS you want to run on. Otherwise, stop believing that OS is relevant, and be suspicious of any online source that claims it is.
Using a lower level GL version is not a magic solution to make a program run everywhere. The number of devices that don’t support GL 4.x are vanishingly small, and even smaller the farther back you go. Any such device you encounter in the wild is likely at least 10 years old, has never been updated, has never been patched, is riddled with security holes, and is probably held together with sticky tape and rubber bands. Do you really want to support running on such a device? It’s not unreasonable to demand a somewhat modern driver on somewhat modern hardware.