Swollen eyes can be fixed when you use ice to dip on it for 5 to 8 minutes.
Of course it is easier for you when you have an eye pad in the fridge or freezer.
For double eyelid you can use those double eyelid stickers. But I don't think it is a good idea because it might be uncomfortable.
Actually I find single eyelid is as nice as double eyelid, so you really don't have to do extra things to change it.