Bohr's model cannot explain the emission spectrum of

Among the following,which transition in the hydrogen spectrum would have the same wavelength as the Balmer transition,$n=4$ to $n=2$ in the $He^{+}$ spectrum?

Based on equation $E = - 2.178 \times 10^{-18} \ J \left( \frac{Z^2}{n^2} \right)$,certain conclusions are written. Which of them is not correct?

When an electron jumps from $n = 5$ to $n = 2$ with all possible transitions,which of the following statements is correct?

If a hydrogen atom is excited by an energy of $8.4 \ eV$,what will be the number of spectral lines emitted?

What is the work function of the metal if the light of wavelength $4000 \, \mathring{A}$ generates photoelectrons of velocity $6 \times 10^5 \, ms^{-1}$ from it? ............. $eV$ (Mass of electron $= 9 \times 10^{-31} \, kg$; Velocity of light $= 3 \times 10^8 \, ms^{-1}$; Planck's constant $= 6.626 \times 10^{-34} \, Js$; Charge of electron $= 1.6 \times 10^{-19} \, C \, eV^{-1}$)