Interview process level goes from basic to medium.
Understanding of basic concept
Most of the time recruiter try examine problem solving skill of candidate
Simple coding questions will be asked , you can consider leetcode basic questions.
My Interview was most of about the Projects I had mentioned in my resume and the interview round 1. Technical => 1.5 hr and 2. HR => 30 mins
What to study ?
C, C#, Object Oriented Programming , Basics of Multi-threading