Noneof these are straight forward. You have not specified whether the contract is for goods or services. Not that it changes the fact that contracts made with minors are voidable at the minors option.
If a minor exercizes his right to void a contract he cannot keep the object of the contract. He gets his money back, the merchant gets his product. The merchant may even have an equitable remedy, enforceable not in contract but in equity.
The fact that a minor fraudulently represents himself to be over the age of majority does not change the fact that as a minor the contract is voidable, but does not mean that he may not be liable for damages under some theory of fraud.
No one is CONSIDERED a party to a contract who is not in fact a party. The mere presence of a parent does not make them a party to the contract. I am not sure what you mean by “conplicit” or complicit. Do you mean they acted as guarantor or actually became a party to the contract?
I will leave it to someone else to discuss performance and partial performance of a personal services contract.
May I suggest you get in touch with NYRA or another youth rights organization and see what you can do to help them out? You’d like to be able to hold minors to contracts; they’d like minors to be able to enter into contracts.
Well, the surgery typically is going to take place in minutes/hours, and I would rather not have the animal in my possession without a signed release. The litigious nature of our society is why I would rather turn the business away.