Can I install virtual adapter programmatically?
In general yes, but I should note that this is not easy if you intend to support different Windows.I’m also not sure if it is possible on NT 4.0 at all.
Can I install 2,3…5 adapters in one system and set different MAC addresses for each adapter programmatically?
You can create more than one network device within single virtual network adapter driver. So the amswer is yes, but requires additional work.
Virtual adapter supports frame length > 1514 bytes for 802.1p/q standards?
VirtNet emulates 802.3 device, however you can create driver to emulate any kind of network device.