What is the ratio of the radius of the second Bohr orbit to the first Bohr orbit of the $H$ atom?

The statements
$i$. In filling a group of orbitals of equal energy,it is energetically preferable to assign electrons to empty orbitals rather than pair them into a particular orbital.
$ii$. When two electrons are placed in two different orbitals,energy is lower if the spins are parallel.
Are valid for

The ground state energy of a $H$ atom is given as $-13.6 \, eV$. The energy of the second excited state will be .......... $eV$.

When the electron of a hydrogen atom returns to the $L$ shell $(n=2)$ from shells of higher energy,we get a series of lines in the spectrum. This series is called:

For ionising an excited hydrogen atom,the required energy in $eV$ will be -

If the radius of the second Bohr orbit of the $He^{+}$ ion is $105.8 \, pm$, what is the radius of the third Bohr orbit of the $Li^{2+}$ ion?