For making hyper casual games in Unity knowledge of the C # language and the engine itself is required at a sufficient level to work. For Unreal Engine - developer - C ++ \ Blueprint. Algorithms and data structures, trigonometry, discrete mathematics, higher mathematics are actively used (all this needs to be tightened up before employment).
There are many specializations, but they mostly make sense for large companies. In small studios, a wide profile is preferred. In development, you can deal exclusively with code, some isolated game mechanics, or in general analytics and services.
Before getting a job, you should learn how to draw up a resume and write cover letters. A cover letter is a way of identifying that a person is not bulk mailing. A very important skill that many beginners neglect.
Usually, candidates with no experience are given a test or asked to demonstrate their project, show code examples. So it will have to be defended as a thesis, explaining almost every line and why it was done that way. This is in addition to the standard set of questions about the programming language and engine. The main thing is not to give up and work on the mistakes that the interviewers point out. In a couple of months / six months / a year, you can tighten up all the missing knowledge and try again.
As an advantage - a portfolio with ready-made projects, experience of working in a team (even in the company of two friends). Any specialist must be competent. The higher the position, the more knowledge and skills he must possess. Junior is no exception. Junior is a specialist who is able to solve most of the tasks on the project independently, in complex and controversial issues, resorting to googling and consultations of senior specialists
The technical readiness of the middle developer is characterized by the fact that, under ideal conditions, he almost immediately begins to perform tasks on the project. He should be familiar with the pipeline of game or application development, confidently own version control at the level: add, remove, commit, push, fix, roll back, resolve conflicts. It is also important to understand the best practices (be prepared to Google them) and have a good knowledge of the capabilities of the technologies and design patterns used in hyper casual games development.