Do you support MultiBit rate streaming LIVE?

Yes totally.

The Dacast player detects automatically the different bitrates of your live stream and allow the viewer to choose between them.

You would need to set it up in your encoder directly. Here's a guide to do it with Wirecast  and with Vmix.

Also, you will need a large enough upload speed to support the multi-bitrates as well (for example, 200 kbps + 600 kbps would be the same as broadcasting at 800kbps and you would likely need an upload speed of over 1MB a second).