For the first question it is because of the reason that,at that time bohr explained what he  exactly found in experiment.In experiment ,he found series of lines of hydrogen spectrum.and thereby gave the correct explaination for his experiment.however has technology increased they found that the series of lines of hydrogen spectrum can be further spilt into many collection of several lines very close together(known as fine spectrum)                                                                     

 ZEEMAN EFFECT is defined as " if a substance which gives a line emisssion spectrum is placed in a external electric field,its lines get spilt into a number of closely spaced lines .this phenomenonis knoen as stark effect .this effect can be explained by MAGNETIC QUANTUM NUMBER ,if a strong magnetic feild a sub shell is resolved into number of diffent orintation in space, these orientations are called as orbitals have slight difference in energy thus explains the appearence of addititonal lines in atomic spectra