For the first one you have to have been promoted and met the CEO (Dwayne), you must also still be on Cassidy's route and not have finished it and according to the wiki you must not have had sex with Aletta, unsure if I had done this or not when I triggered it. You must also have had sex with Lexi already, if you meet these requirements then if you work in the office around 12-16 you'll get invited to a party at the nightclub with Dwayne + Aletta, once there Lexi will join you and you'll have a foursome. Unsure on the options but I believe Dwayne will ask to sleep with Lexi and you get the choice of saying yes or no to this. Saying no will result in you fucking Lexi while Dwayne fucks Aletta. I didn't try saying yes last time I did it but my guess is if you say yes you'll instead fuck Aletta.