n British English, you can use the idiom "jump the queue" when someone goes in front of other people who are already waiting in a queue.

We use the idiom "cut in line" when someone goes in front of other people who are waiting in line.

The ins and outs are the complicated details or the special peculiarities of something. The term can also refer to the complex elements of a process.

A poster child is a representative example of a situation, quality, or activity. It can be: a person, a group of people or things, an organization, an object, a concept, an idea, a theory, etc.

Pushing on a string means that your strategy, despite investing all your energy and efforts, is not working. In other words, you do not succeed in achieving your goal because what you are doing is ineffective.

To no avail means that you do not succeed in achieving your objective, or what you do is ineffective.

If you do something for the sake of it, you do it for no particular reason. There is not a motivating cause. You do it just because you want to.

To turn on a dime is to change direction quickly (literally or figuratively). This expression can describe strategies, mood, psychology, attitudes, prices, or many other things