1. Period and frequency, definitely. (Especially since one is just the reciprocal of the other!) A change of refractive index doesn't affect either one.
2. Period and amplitude, no, because there is some reflection at the boundary if the refractive indices differ.
3, 4. Definitely no, since velocity and wavelength change if the refractive indices differ.
Sound is propagated in the form of longitudinal waves. When sound travels from one medium to another, both its velocity and wavelength undergo changes. The velocity of sound in a given medium is obtained by the equation v=nW, where 'n' is the frequency of sound and 'W' is its wavelength in that medium. Velocity of sound is directly proportional to the wavelength.
Thus, if the velocity of sound doubles when it travels from one medium to another, its wavelength also doubles. The frequency of sound depends upon the source of sound, not the medium of propagation. Hence, it does not change.