1) I did wajib ghusl but I have doubt whether I washed my right feet or not. Is my ghusl valid?

2) If i have two ghusl niyyat in mind and one I'm in doubt and other ghusl I am sure about performance then it will be valid if i make such niyyat?
eg- one niyat i have for for jumma ghusl on Friday, which i am sure that it can be performed, and other ghusl is janabat, about which i am not sure whether its wajib in me or not, but as a precaution im make a niyat and do ghusl with both intention, then ghusl will be valid?

1) Yes your Ghusl is valid. If doubt arises in the mind after ghusl as to whether ghusl was correct or not, then there is no need to do Ghusl again.

2) Yes you can have many ghusls Niyyat at a time but no need to do different Ghusl for each one rather you can do many Ghusls with one Niyyat. If you have doubt (and have no sign of Janabat) whether it’s wajib on you to perform Ghusl Janabat or not then there is no need to do Ghusl.