It can support all the areas supported on the mentioned range for areas, but you should have robust devices being the DR and BDR to avoid any performance impact. But to be honest I never have seen all the areas connected to the backbone. 4294967295 (not including the area 0 otherwise it should be 4294967296 areas)
Plus all the combination for the other format used in OSPF areas: A.B.C.D
220.127.116.11 to 255.255.255.255
Please check this link: https://learningnetwork.cisco.com/thread/6149
Hope it is useful
the theoretical limit of 4,294,967,295 will likely never be reached anywhere in a real network. The amount of areas connected to a backbone depends on things like the size of the link state database, the amount of routers in the area(s), all that will weigh on CPU and memory. These are going to be your limiting factors.
50 is indeed best practice, as the link state database can become unstable otherwise.
Is this an exam question ? If so, stick with 50. In reality, there is no hard limit, as it also depends on what area you configure (NSSA, Stub, normal)...