The different electron energy levels caused in hydrogen cause these lines in the spectrum to be produced in this way because the wavelengths that are released when the electron move back to the ground state is specific and it varies accordingly.
2. Into which energy level are electrons dropping into to make these visible lines?
The electrons are dropping back to the ground state which is the bottom most energy level to makes these visible lines.
3. What happens when the electrons drop into the 1st energy level? What happens when electrons drop into the 3rd, 4th and 5th energy levels?
The wavelength of the electrons becomes closer together and smaller as the electrons drop into the 3rd,