Salaah

Omitting one's Salaah and performing it as qaza due to one's job

Q: I recite quaran daily in the morning without fail. Also I had started salat but unfortunately I can not perform five time salaat on time because my job is like that. So whatever time of salaat I get, I perform it. Like I came early home so I perform magrib and isha. So my question is that how can I perform Salaah on it's proper time or else I have to perform kaza namaz.

Sitting and performing Fardh and Waajib Salaah without a valid excuse

Q: If a person prays a fardh or waajib  prayer sitting down, without a valid excuse, is his prayer considered invalid? I recently heard from a Mufti that the prayer itself would be valid, since he did not miss a fardh element of prayer by sitting down (and not standing). What is the position of the Hanafi madhab in this regard?