Hi,

To work with versions you could use IContentVersionRepository:

var repository = ServiceLocator.Current.GetInstance<IContentVersionRepository>();
var id = 123;
var versions = repository.List(new ContentReference(id));

i dont have id of the version. i only have page reference in backend now i want to get current version of the page that is being displayed to editor or publisher when they click on the page in site pages tree list

So you could use Id from your PageReference:

var pageReference = ....

var repository = ServiceLocator.Current.GetInstance<IContentVersionRepository>();
var versions = repository.List(pageReference);

it will return all versions of that page. i want to select current version of the page(it can be or cannot be the latest version) among these versions

The answer is 

var commonDraft = versionRepository.LoadCommonDraft(page.ContentLink, "en");