Pre-sales questions

I have some questions to know if I can buy your product:

1) I want add only "time" limit download not "number" limit download. The user after buy my product can download without limit my product until her subscription is end. Is this possible?

2) I want add "upgrade" limit to my products. For example the user can buy the product B only if he has already bought product A. Is this possible?

3) If 2) is possible can I set a option like: the user must have a valid subscription or the user may not have a valid subscription?

4) Works with your ACESEF?

5) Works with last version of VirtueMart?

Thanks