I would advise to tell the truth and say it was nikkah. If you classify it as rukhsati then you need solid proof of AFTER your rukhsati which you probably don't have and normal dress wearing wedding wont work with embassy as they already know how extravagant our weddings are. keep record of EVERYTHING. bday gifts, call logs, emails, use viber and whatsapp since you can get a documented email of your history. I recommend making a folder and backing up data every 2 months or so. whatever YOU think is a proof is probably a proof and will make your file fat incase they object. Rest Allah knows best.