Options delta

CFA Level III Derivatives
#1

for synthetic long call, delta goes from 0 to +1, gamma is positive, under what circumstance will delta go from +1 to 0?
for synthetic long put, delta goes from -1 to 0, gamma is positive, under what circumstance will delta go from 0 to -1?

#2

We usually talk about delata of oprtions from long perspective.
But
+1 to 0 - short put
0 to -1 - short call
draw the diagrams

#3

so the opposite way is for shorts, thank you!

#4

note the options chnaged too