Reraising a bigger pair on 3rd(no hand)

[Sinnister]

Hello, all, as some of you may know I am new to stud and in reading 7sfap I am not sure if I understand one concept fully. If I hold (9s,Kd)9d and a ten raises, if I am sure I can get it heads up this this a mandatory raise if my cards are all live as well as my suit, or must I have doubt about his holding. In other words If I know 100% he has a pair bigger than 9s but I have live oc plus flush card is a reraise automatic here if I can get it heads up or is this a losing play?