Hmm well demisexual means that a sexual attraction can only be formed once there is a strong and positive emotional bond with a person. How long it can take for a demisexual to feel sexual attraction varies.
Someone who is demigender has a partial connection to a certain gender (varies by person). I'm not demigender so I'm not be best at explaining this one.
https://gender.wikia.org/wiki/Demigender