Hi,
maybe it's the time but I can't see why White's response for Black 1 prevent's Black from cutting (cf. p. 9). I've attached the diagram and my thoughts on White's responses. I am pretty sure I'm missing something obvious, but obviously can't see it

. Hence, any hints are appreciated.
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[White]PB[Black]AW[ob][pb][qc][rc][rd][qf][qg][rh][ri][rj]AB[pc][pd][qd][pe][pf][pg][qh][qi][qj][qk][rk]LB[qc:A][rh:B]C[Initial position. Black to separate A and B.]
;B[re]
;W[sg]LB[re:1][sg:2]C[For me, B1 works (at least regarding W2, which is the point of this question), as I will show in the different variations.
]
;B[sf]SQ[sd][qe][se][rf][rg][sh][si][sj]C[We will consider all marked possiblities for W's next move.
It seems essential to prevent B's connection at R15 but I'll look at non-obvious moves, too.
]
(;W[sd]
;B[qe]
;W[se]
;B[rf])
(;W[qe]
;B[rg]
;W[rf]
;B[rg])
(;W[se]
;B[rf]
(;W[qe]
;B[rg])
(;W[rg]
;B[qe]))
(;W[rf]C[Good idea?]
(;B[se]
;W[qe]
;B[rg])
(;B[qe]
;W[se]C[But B will not play like this

]))
(;W[rg]
;B[qe])
(;W[sh]
;B[qe])
(;W[si]
;B[qe])
(;W[sj]
;B[qe]))
Cheers,
mic
Go is easy: don't play bad moves.