If I'm fly business class do I have to pay to access the busniess class lounge in Dubai?
No you don't pay ... you qualify to get in just by flying business class.
No, you dont have to pay to access Emirates Lounge and also you can take advantage of their Chauffeur service. Though you cannot access these features if you have upgraded to business class through special promotion offer by Emirates during check in or in email.
Of course not, and all the information you need will be in manage my booking and on the Emirates website as to whats available when travelling business class.
But as stated above, not if you have been lucky enough to of been upgraded