Yes to both, but MH is not the designated lounge for QR J class pax (and the MH lounges are busy at 9pm before all their evening departures; and dire at 2am, when the aircon is turned down, bar is closed and cleaning starts); you may need to find a QR transfer desk to get an invite to the Plaza Premium First lounge (not to be confused with the larger Plaza Premium lounge) - it's much smaller, but at least you can get an a la carte meal and alcohol from the bar
Although tbf, with such a long layover, you may as well pop into the city to get a nice dinner somewhere (or lounge hop - don't forget there's CX too in the early evening - not particularly luxurious, but very peaceful after the last KA departure)