Answer is 21 spaces.

with just 1 spoke, there is one continuous space.
2 spokes devices the circular space in 2 spaces.
with 3 spokes, 3 spaces.
with 4 spokes, the space is devided into 4 90 degree pies. 
..
..
..
So with 21 spokes, 21 spaces.

Yes. . (2 ^ 6 – 63 = 1)
2^6 = 64
64- 63 = 1

The answer is : At the end of 59th minute.

If the bacteria doubles every minute and if by the end of an hour (i.e. 60 minutes) the jar is full, then by the end of 59th minute the jar must be half full so that within a minute, it can double to fill the jar completely.