Attached Link: What Order and How To Install V4.2

Also P7  on Mac here-

(I backed up my Runtime first just incase.) On the Daz site it's recommended that you delete the earlier versions.... but I had  put my V4.1 in a  new character folder other than the Daz People one and when I installed V4.2 a new Daz People folder  appeared with the new cr2s inside.   I had deleted the V4  cr2 a while back anyway as I preferred V4.1. but the cr2 is all I  deleted. Not the obj.
So you could put your V4 in another folder if you want to keep her around for a bit.

Anyway so far I have had no problems with keeping the V4.1 cr2 in my runtime as well.  I did  it as a 'just in case' .. But do look at Daz's suggestions about  the order of installing the Morphs++, Creature Morphs etc. I did do it their way and it all is working fine for me.   
 Remember to run the Update Script after you install her. That makes all the difference !

" Try and be nice to people, avoid eating fat, read a good book every now and then, get some walking in, and try and live together in peace and harmony with people of all creeds and nations."
-Monty Python