1. connect MTR to win over usb. sd card instantly recognized.

Pretty much every hardware MTR released over the last decade will do this. Both the ones that do and the few that don't allow for the removal of the SD card and insertion into your CPU and the card is read and accessible either method as mass storage. The cards are formatted with proprietary method that partitions the card so the proprietary files and folders are separate from a section partitioned so PC's can access the card and folders needed to transfer data between the two devices.

2. in win set up new folder. rename win folder to song name.
Yes. Folders can be created, deleted and renamed in windows the same as any mass storage device.
There may be some folders required by the MTR device that can't be renamed.

3. open biab. and arrange song in biab with guide bed tracks.
No hardware MTR will do this. To my knowledge, at this time, no MTR is setup to accept the BIAB VST but that is something that can be done with some MTR devices.

4. export guide stereo song mix from biab to song folder
from step 2.
Yes. Even the most economical MTR devices can do this as well as export/import individual tracks.

5. copy to MTR sd card the guide stereo mix (bed tracks) from the win song folder using mousey..
Yes.

6. record added tracks in MTR on the MTR sd card .
vocs/other instruments/whatever synced with the guide stereo mix now on the MTR.
all in sync.
Yes.

7. when all finished on MTR, copy MTR tracks back to win song folder.(from step 2).
using mousey , so now we have in win song folder the biab stereo song guide wav. plus the MTR recorded tracks. (plus the little txt win text settings file.)
Yes

8. now individually export each real track and/or midi from biab to the same win song folder. wav's and mids.
Yes

9. open up ones favorite daw. reaper/cubase/RB/mixcraft whatever floats your boat.
and import all biab tracks and MTR tracks from the win song folder.
Yes. It recognizes the SD card either connected through USB or direct insertion into the PC.

10. arrange and test mix to taste using whatever plug ins float your boat.
Yes. MTR tracks are audio files recognizable by all DAWs.

11. do final stereo mixdown in daw etc etc.
Yes. MTR tracks are audio files. Files can also be created and imported from the DAW to the MTR for mixdown and mastering by the hardware MTR.

12. DONT FORGET BACK UPS JUST IN CASE.
Yes. Every MTR I'm familiar with has backup/restore capability.

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.