Mirroring begins with eyes and if the Alternate's view is obstructed, they are unable to establish the telepathic connection. The telepathic connection is vulnerable to telepathic influence, meaning that another telepath could prevent the Alternate from completing the download. A sudden break in focus would similarly disrupt the telepathic connection.
The information which the Alternate receives is imprecise. The Alternate cannot actively seek out specific information. The data the Alternate obtains is about what they have mirrored from the victim, like how to read sheet music or the limits to their new ability.
When the Alternate first learns a new skill or ability, they will experience a mental impression of how the victim felt at that moment. When the connection is broken, they will no longer experience what the victim feels. The Alternate does not 'feel' the emotion, rather, they piece together the emotion from the thoughts of the victim. The Alternate can only mirror one person at a time, and whenever they mirror a new victim, they lose all data downloaded from the last victim.
NOTE: This power is currently Restricted in the Role Play.