First off
PozativeR8 figures are quite accurate and i would also say on the conservative side. The selection process not a walk in the park, you must be well studied or you will be going home just as soon as you arrive.
Do QR provide laptop for new joiners with cbt and company manual included?
NO, your responsible to make sure you have the tools to accommodate.. (i.e. your own laptop)
Do you fly economy or business to the interview. And what hotel do candidates usually stay?
Business class usually, hotel are dependent on hotel space available in the country, but these days it's usually the Qatar Airways Oryx Rotana Hotel. it also could be anywhere in the city, Marriott, Ramada, Sheraton.. etc..etc.. it's not a big city and transport will be arranged so it does not matter where you stay.