Project success criteria are the standards by which the success of a project is judged. They include specific goals, deliverables, and performance measures such as cost, time, and quality targets. Defining these criteria during the initiation phase provides a clear understanding of what constitutes project success and guides decision-making throughout the project lifecycle.
Per the CompTIA Project+ PK0-005 exam objectives, under Domain 1.1: Explain the basic characteristics of a project and various methodologies and frameworks used in IT projects, establishing clear success criteria is fundamental for project planning and evaluation.

A cost-plus contract is a type of contract where the buyer agrees to reimburse the seller for the actual costs of the work plus a fee, which can be fixed, percentage, incentive, or award based. This type of contract has the highest risk for the buyer because the buyer has no control over the cost or quantity of the work and the seller has little incentive to control the costs or complete the work efficiently. The seller may inflate the costs or prolong the work to increase the fee. The buyer may end up paying much more than the estimated budget or the market value of the work. Reference = CompTIA Project+ PK0-005 Certification Study Guide, Chapter 9: Project Procurement Management; CompTIA Project+ Certification Exam Objectives, Domain 3: Project Execution, Objective 3.3: Execute procurement activities.

Scrum is an Agile framework that is well-suited for projects with rapidly changing requirements. It operates in iterative cycles called sprints, allowing for regular reassessment and adaptation of project goals. This flexibility makes Scrum ideal for environments where the company's strategy and product requirements evolve frequently, as it facilitates continuous improvement and responsiveness to change.
According to the CompTIA Project+ PK0-005 exam objectives, under Domain 1.2: Compare and contrast Agile vs. Waterfall concepts, Scrum is highlighted as a methodology that supports adaptability and iterative development.

Obtaining approval for changes to software is crucial to ensure that the changes do not negatively impact other functionalities of the software. Approval processes typically involve a review that assesses the potential impacts of the change, which helps in mitigating risks associated with the change.
References = The answer is based on standard project management practices and the typical use of change control processes in software development. For detailed information, please refer to the CompTIA Project+ Study Guide and other official CompTIA resources.