DURING A VECTORED ARR; THE FO OF A DC9-30 DSNDED IN RESPONSE TO A TCASII RA; RIGHT AFTER COMPLYING WITH R 90 DEG TURN GIVEN BY APCH CTLR; FOR A TFC CONFLICT AND CTLR CONFUSION OF ALT ASSIGNMENT. AFTER LEVELING OFF; A B757 CROSSED OVERHEAD AT 200 FT. THE CTLR BELIEVED THAT HE HAD ASSIGNED RPTRS A LOWER ALT.

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WE WERE BEING VECTORED TO A VISUAL RWY 12R AT MSP AND DSNDING TO 7000 FT. AT 7500 FT; CTLR STATED 'EXPEDITE DSCNT; TFC AT 1-2 O'CLOCK POS; 7000 FT; B757.' WE LEVELED AT 7000 FT; OUR LAST ASSIGNED ALT. I ASSUMED ATC WAS CLBING THE B757 BECAUSE HE HAD TOLD US TO EXPEDITE TO 7000 FT. ATC THEN SAID 'ACR X; EXPEDITE YOUR DSCNT.' I SAID; 'WE ARE LEVEL AT 7000 FT; THAT'S OUT LAST ASSIGNED ALT.' AT THAT MOMENT; THE AMBER '00' WERE COMING IN FAST FROM 1 O'CLOCK ON TCASII. ATC GAVE US A HARD R TURN TO 90 DEGS; TCASII GAVE US A DSNDING RA. FO WAS FLYING AND COMPLIED WITH RA; AT 6600 FT GAVE US A 'CLR OF CONFLICT.' AN ACR Y B757 PASSED AT 12 O'CLOCK POS; 200 FT VERT; 1000 FT HORIZ. PAX WERE AWARE OF MANEUVER AND SOME SAW THE B757. ATC SAID HE HAD GIVEN US 4000 FT; BUT 'MUST HAVE BEEN BLOCKED.' WE NEVER HEARD OR ACKNOWLEDGED 4000 FT. THE REST OF APCH AND LNDG UNEVENTFUL. THE CTLR WAS VERY BUSY AND SEEMED LIKE HE WAS BEHIND THE CURVE. LATER FOUND OUT HE WAS A SUPVR. SUPPLEMENTAL INFO FROM ACN 416015: AS WE PASSED THROUGH 6600 FT WE STARTED RECEIVING MORE VECTORS FROM ATC (EITHER 090 DEGS OR 120 DEGS) BUT WE WERE UNCLR BECAUSE THE CTLR APPEARED TO BE CONFUSED. WE READ BACK 090 DEGS AND RECONFIRMED IT WITH THE CTLR. HE ALSO MADE A COMMENT THAT HE HAD GIVEN US 4000 FT; BUT IT 'MUST HAVE BEEN BLOCKED.' WE NEVER HEARD 4000 FT AND NEVER READ IT BACK (TO THE BEST OF MY RECOLLECTION).