To show Component as a related list on Product, a lookup relationship on Component to Product should be created. A lookup relationship creates a loose association between two objects and allows users to relate records from one object to another. A lookup relationship also allows users to add the related list of the child object to the parent object's page layout.

For tracking whether contracts have been sent for Opportunities:
D . Checkbox. This field type allows users to clearly indicate (Yes/No) whether a contract has been sent. This binary nature of checkboxes makes it simple to filter and report on Opportunities based on whether a contract was sent.
Steps to configure this field:
Navigate to Setup → Object Manager → Opportunity.
Click Fields & Relationships → New → Checkbox.
Define the field with a label (e.g., Contract Sent).
Set the default value to false (unchecked).
Add the field to the relevant page layouts.
This setup facilitates accurate reporting and ensures that opportunities cannot be marked as "Closed Won" without indicating whether a contract was sent.
For guidance on creating fields, see Salesforce's documentation on Custom Field Creation.