doubt about Il2 and flying circus with Steam

[AhnSuyeong]

Hello

apologize if someone already asked this before, but i can't find in the forum. My question is, if I have il 2 Sturmovik: battle of stalingrad bought through Steam, can i buy il2 sturmovik: battle of moskow in the website?. and if i want to buy Flying Circus, can i also buy it through the website if i have a steam account? how can i after link the games? 

Sorry for my english (it's not my language), thank you for the answers and merry christmas ^_^