Thanks for taking time and putting the questions.
1. This feature is possible for eProducts only as of now. Moreover, It hasn't been included in the current version due to some reasons.
2. As of now, No.
3. As of now, No. What is the aim of this functionality?
4. As of now, It can be in only one language. We would be able to complete full backend and frontend translations by 1.4.9.
5. Not Possible until Sellacious 1.4.9, We are in process of linking Sellacious categories with Joomla! categories. Whenever that thing is done, Native Joomla translation would do the thing.
Please note that, Though many of things are not possible, They might be arriving in Sellacious soon (except #2, Which is not on our roadmap).
PS: For a fee, We push some of our development tasks according to the needs of our customers.