Versioning is two problems. If it is a block of requirements, then cloning the block works ok in conjunction with setting a package Baseline. For individual elements, the Time Aware modeling offers some help https://www.sparxsystems.com/enterprise_architect_user_guide/15.1/model_domains/time_aware_models.html
Also, TAM is a promising concept, however please evaluate what your plans are when it comes to reconciliation, or compare / merge with existing requirements. Baselines, are good ways to keep track of requirement versions, however if you intend to have a branch / copy of requirements as they are been developed and plan to merge and reconcile, i would suggest Baselines (Especially with 15..1 where you have ability to connect Baselines to a shared repository) or RAS.
A short video (not fancy) that I did to showcase RAS and baselines for one of our clients