WhatsApp messenger in Tizen store unable to install on Samsung Z2

Hello,i deleted the old version whatsapp in my samsung z2 phone and now when um trying to download and istall another one from tizen store it doesn't want its just telling me that its not supported.another problem that i have i can't install any other apps from uknown source its telling me that my phone is blocked to install apps from unkown source.pease help me out