Here are the answers to your questions:
A) What is the objective of the testing phase in a software development life cycle?
Answer: to check whether a software is working as intended
A) What is a functional test?
Answer: a test that checks a specific feature within a program
A) What is the difference between unit tests and integration tests?
Answer: In unit tests, each module is checked independently, whereas, in integration tests, all modules are combined and checked.
A) Under what condition would a unit test be applied?
Answer: when we want to verify each unit independently
A) When is an integration test needed?
Answer: when we intend to check logically integrated modules