The job market is very tough right now for all sectors. It is unfortunate that you haven't had any luck so far but here are some tips that you may or may not already know.
(1) Quality over quantity. As you have mentioned, a lot of companies only allow one application per year so you need to make the most of it when you apply. Make sure you tailor your CV by looking at the job requirements and adding any that you meet to the CV. Like for example if I was applying for a robotics position, I would edit my CV and write about that if I did it in university. This will make you stand out when they are shortlisting CVs
(2) Do practise video interviews and psychometric exams. A lot of the video recording questions will be very similar so just google search for them. One example of a common question is "why do you want to work for us?". Same thing with psychometric exams, just look online for free tests.
(3) Set yourself a daily target on how many jobs you are going to apply. Don't make the number too big or too small, set it to like 5 per day and keep to that target until the jobs you want run out then do like 1 every other day.
(4) Relax, do not let the fact that you do not have a job yet define you. You are not a failure and you will eventually get a job. Remember to do other things such as hang out with friends or hobbies.