In the atomic spectrum of hydrogen, the spectral lines pertaining to electronic transition of n = 4 to n = 2 refers to

What will be the number of spectral lines in infrared region when electron transition occur from n=7 to n=2 in hydrogen atom :

The shortest wavelength of the spectrum line is that of electron being transits into atom to ion from n = 2 to n = 1 for .......

What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition, n = 4 to n = 2 of He+ spectrum?