No, there is no semester system in IGNOU for BA courses. In IGNOU students are enrolled in two cycles (January and June). The submission of assignments and TEE (Term End Examination) is scheduled once a year.
Although assignments can be submitted only once a year, there is a high chance that if you fail to appear in May or December TEE, you can appear for that particular subject on another cycle.
For example, you enrolled in this course in 2021. If you wish to appear for June 2022 TEE, you are required to submit the assignments by March 30 2022. If you fail to appear or pass the TEE, you can appear for the same exam in December 2022.