Is this the same sign as 'fake'?
No, the sign for 'fake' is different. 'Fake' typically involves brushing the side of your index finger past your nose. 'Hypocrite' specifically uses the layered hands to show a false front or covering up.
Can this sign be used for 'imposter'?
Yes, because the sign conveys the idea of a false front or hiding one's true identity, it can often be used in contexts where someone is acting as an imposter or pretending to be something they are not.
What facial expression should I use?
Since 'hypocrite' has a negative connotation, your facial expression should reflect disapproval, frustration, or disappointment. A neutral face might confuse the viewer about your intent.