Nikaah & Marriage Issues

Would a couple be responsible if they don't know hurmat-e-musaaharah was established?

Q: Would a couple be responsible if they don't know that another person has impacted their marriage? For example, (may Allah protect us all from this) if a daughter touched her father with lust but neither her father or mother know about this, would they be responsible? Would the daughter be sinning if she doesn't tell them as it could have disastrous impact on the family? Would her parents be sinning as they don't know? 

Is an erection required for hurmat-e-musaaharah?

Q: A generic question about "hurmat e musahara". I know lust is defined as the erection of the penis. Does slight movement in the penis, similar to what happens during kegel also cause hurmat e musahara when erection does not properly occur/no full erection occurs. I get anxiety and I'm scared. I'm more or less certain that I've never had a proper erection while touching my mother, but at the same time I'm scared of slight movements in the penis that may have occurred in the past - movements that may have occured due to my mental condition. Especially since the idea of potentially negatively impacting my parents is often on my mind when any physical contact occurs with my mother. A slightly detailed and clear answer on this issue could make the matter clearer to me as often I'm not sure what constitutes lust and it makes the matter tough for me. I'd like to think that I do not in any way want to engage in intercourse with my mother and the idea is reprehensible to me. It's after I started reading fatwa on these that these thoughts have significantly started bothering me. 

Fantasizing about a man

Q: If a unmarried girl imagines having intercource with her future husband, is she sinful? She is not engaged yet. She doesn't imagine any face of a man and doesn't imagine any private part of a man. She just think that she will wear a western dress and present herself to her husband. And she imagine her husband will play with her private parts. She does not touch her private parts during imagination. She just fell on the bed and started imagining that she is with her future husband. Does this count as masturbation? She does this practice once a day. She reaches her climax point during the imagination. Is she doing a haraam? Her parents are trying to get her married but not success yet.

Court marriage

Q: I want to know if a person gets married without the consent of their parents (means court marrige). Both parties are mature people and the people present at the time of the nikkah were the lawyer and 2 friends. They didnt sign the nikkah nama as witnesses whereas there are signatures of unknown people who were not present there at the time of the nikah, so is this nikah valid? So the nikah took place in court as it was a secret nikkah and there was no wali present. it was just the groom, bride, 2 female friends of the girl, 1 lawyer and 1 molvi to perform the nikah. The marriage was registered. But on the nikah nama as a witness 2 unknown people signed who were not present there at the time of nikah. So is this nikah valid?