<< Please tell me if i need to order this laptop in advance or if i can buy it at the store when i visit Dubai for a day. I will pay in cash. >>
So sorry, I was so engrossed in the technical aspects, I did not internalize the process you were proposing to make the purchase.
• Apple does not accept orders from outside the country of delivery.
• Orders must be prepaid using locally-acceptable payment methods. Check with the store to see about cash. (credit cards are checked, but not charged until delivery).
• While Apple has gotten really good at predicting delivery times, those times are not guaranteed. Standard policy in the US is that your goods will only be held for one week, unless you make other arrangements. Your one-day stopover may simply be too tight for this to work.
• Macs sold in Russia are said to be pre-loaded with government-issued spyware so that your activities can be tracked. Be sure you can get your new Mac back into the country before you spend a lot of money, and then get it impounded when re-entering the country.