2011 ACURA TSX Power Train Problems

7 F, CAR WAS PARKED OUTSIDE ALL NIGHT, STARTED CAR, WAITED A FEW MINUTES, BACKED OUT, BRAKES NORMAL, DRIVING FORWARD SLOWLY, BRAKES NORMAL, WAS GOING 30 APPROACHING STOP SIGN, WENT TO BRAKE, PEDAL WAS SOLID...NOTHING WAS UNDER THE PEDAL, BUT FELT LIKE THERE WAS A BRICK UNDER THE PEDAL. OBVIOUSLY I DIDN'T STOP, THANK GOODNESS NO CARS WERE ON THE ROAD. I SLOWED DOWN EVENTUALLY, THEN PUSHED EXTREMELY HARD ON THE PEDAL AND WAS ABLE TO BRAKE. THEN AFTER DRIVING VERY SLOWLY & TESTING HARD PEDAL, THE PEDAL ACTED NORMAL AFTER A FEW MINUTES. NORMAL PEDAL NOW. ON A SEPARATE PROBLEM, THE TRANSMISSION HAS BEEN DOWNSHIFTING ON ITS OWN, I'M DRIVING ALONG, AROUND 45 MPH OR SO, THE TRANSMISSION IS IN D, DASH LIGHT & SHIFTER IN D, THEN EVERY NOW & THEN THE TACH WHINES, THE TRANSMISSION DOWNSHIFTS & SHOWS A LOWER GEAR (LIKE 4 OR 2 OR 1)...