As a Beginner in Back-end can I get to work as a Junior or Senior Back-end Developer
This post answers the question to beginners trying to get employed in the web development positions.
You are not entitled to reward designation upon yourself even before getting employed! It's the choice of the employer to give you a title or designation based on your job role.
In your resume, you just need to mention your skills if you don't have job experience. As regards your level of knowledge goes, it depends on your portfolio and the job requirements of your employer.
If your portfolio matches the requirements of a Senior backend developer, then, they may accept you for this job designation.
While applying for job roles, in the beginning, it's always better to look for a junior level rather than a senior level, as you don't want to end up being embarrassed in the interview when you cannot answer challenging questions targeted at senior level developers.
I hope, this answers your question.