(a) That's wrong. Specific performance is a remedy which originates in equity and, as such, it is only available when the court thinks that a common law remedy (particularly an award of damages) is insufficient to do justice. Additionally, a court will only order specific performance if enforcing the order is likely to be practical. Accordingly, the courts will not order specific performance of duties that require goodwill or cooperation, because it is impossible to force people to carry out their duties in the right spirit. Nor will the courts involve themselves in supervising performance that is to take place over a long period, because the burden of supervision becomes too great.
See Lumley v Wagner and JC Williamson v Lukey.
For these reasons, it is unlikely that the courts would grant Tyler an order of specific performance requiring that Sunny perform the part of Heroa in the show even though she is clearly contractually bound to do so.
As to the possibility of an injunction, the courts will issue such an order to prevent a threatened breach of the law, or a continuing breach of the law. A breach of contract is such a breach. However, injunctions are issued at the discretion of the court and will not be ordered if the effect of doing so is to require specific performance of contractual obligations that the court would be reluctant to enforce by means of an order of specific performance. That would clearly be the case here, since the breach of contract Tyler wants to avoid is the failure of Sunny to carry out her promises.