On that last part a Jr. CS question that you maybe not even use in real life for some CS jobs. People forget that not everyone is writing awesome ML things or other awesome things you read about in newspapers. Most of the people are writing CRUD code, do some data transformation , automate so simple office process, etc. Never had much use there of Big-O knowledge....

Does not mean I never used much of this knowledge I have needed at some points. But by that tine I had to refresh the knowledge again...