In India, If you learn Sa, Re, Ga, Ma, Pa, Dha, Ni and Sa on a C Major or a C# Major Scale, and your teacher makes you believe that this is the only scale you've to think about in this whole keyboard, then you've been served a lie. Because either he doesn't know WHAT HE'S TEACHING or don't want to tell you more about the scales, so you don't ask many questions.
Sa, Re, Ga, Ma, Pa, Dha, Ni and Sa are similar to the Western do re mi fa so la ti do.
A major scale can be played anywhere on a Keyboard (or alike instrument). The sequence of a major scale is W-W-H-W-W-W-H, where W stands for Whole Step and H stands for Half Step. There are 12 different diatonic major scales, one for each note in the chromatic scale.
TONIC: Root note of a scale.
SCALE DEGREE: Number assigned to notes in a scale. In C major scale it's like this - C(1), D(2), E(3), F(4), G(5), A(6), B(7), C(1). Now these scale degrees can be named differently according to different countries, like in India, it is - Sa, Re, Ga, Ma, Pa, Dha, Ni, Sa. In the United Kingdom, it is - do, re, mi, fa, sol, la, ti, do.
So your "Sa" can be any note on the keyboard. But in some places, the First scale degree can be fixed.