In order:
No.
Yes, natively for the sound card in question. Usually SB compatible, WSS compatible, and GUS. Less commonly PAS. Generic interfaces don't exist in DOS.
No.
VLB cards were supported, usually exposed via VESA BIOS extensions.
Not sure what you mean. Master Control Program?
Yes, it's called an MPU-401 adapter.

dnewhous wrote:

Was MCI (media control interface) available on DOS? This was for watching video. Wave Out? ASIO, as part of the operating syste […]
Show full quote

Was MCI (media control interface) available on DOS? This was for watching video.
Wave Out?
ASIO, as part of the operating system?
Vesa local bus, was it an interface in DOS as well as a bus?
Same with MCP?
Also, was there a MPU-401 or UART interface in DOS?

That's not how DOS works.