Need help with dropdown allowing multiple selections

[wellloaded]

Can someone please shed some light on what would be a right approach to:

• open a dropdown menu (I guess click would do)
• wait for it to open and spot the menu not being populated. This is a peculiar issue of the site I'm using, occasionally it doesn't display the options. (not sure how to achieve this?)
• select 1st 4th,5th,6th,and 7th element only
• close the menu

Any suggestion would be greatly appreciated.

Thanks