How To Proceed With A Very Doubtful Application Sent From A Freelance?

Hi,


A freelance developper has to send me an application he developped for me.


I found this person on internet and don't know much about him.


I highly suspect these files might either be infected or hide a function that transfers data of mine to an external server.


So I really want to make sure that :


1. the files he sends me are not infected


2. the files he sends me can't include a trojan


3. the application he sends me can't communicate with internet to steal information from my PC (this application's should not need internet to work).


How do you recommend proceeding in this specific case?


Thank you


PS : I use Windows 10, 64 bits, and I use Bitdefender Antivirus Plus 2015.


I don't use other security programm or firewall. If I should, feel free to let me know what you recommend.