Can minors, person under 18 years of age, be held liable for their contracts, what types of contracts and what is meant by ratification?

1. On January 5, 2012 a girl met with the landlord for the purpose of leasing on 2 bedroom apartment. A written lease was prepared and signed by both parties. The terms of said lease called for rent in the amount of $850 per month for one year with the tenant being responsible for gas and electric. After signing the lease, she noticed that the apartment’s carpeting was rather worn and stained. He then promised to replace the carpeting within the next two months. After 3 months, he refused to install new carpeting and told her that he had changed his mind. Does she have any cause of action against him for breach of contract? Why or why not? 2. On October 15, 2011, he was in the process of constructing a 27 story apartment building in Chicago. The electrical work was to be done by an electrical contractor. On October 16, 2011 the contractor informed him that he would not be able to perform due to the fact that he owed his supplier $10,000 on an old debt and that the supplier would not tender the supplies now needed until this debt was paid. He worked against deadlines, phones the supplier and promised to pay the contractor his debt within 30 days if he would give the contractor the needed supplies. If he fails to pay this debt, could the supplier enforce this promise? Why? Why not? 3. Can an unlicensed worker enforce her contract should she not be paid for services rendered? Assume work was satisfactorily performed and that the license is required by law. Would there be a difference depending upon what the purpose of the license is for? 4. Can the duties owed by parties to a contract be delegated to third parties who are not part of the original contract and if so under what circumstances?