(chess)thereby?

Hi.
What's the difference between:

Then Black must stake a bigger claim in the center and advance either his c5- or c6-pawn, challenging White's central position and striking out for still more space.
and
Then Black must stake a bigger claim in the center and advance either his c5- or c6-pawn, thereby challenging White's central position and striking out for still more space.
and
Then Black must stake a bigger claim in the center and advance either his c5- or c6-pawn and thereby challenge White's central position and strike out for still more space.
and
Then Black must stake a bigger claim in the center and advance either his c5- or c6-pawn, which thereby challenge White's central position and strike out for still more space.
and

Then Black must stake a bigger claim in the center and advance either his c5- or c6-pawn, when he challenge White's central position and strikes out for still more space.

Thanks in advance