No u do not have to be a cna. You can go directly to be an lpn. An lpn is the same as getting your rn. u dont need to reach each level before you can get to an lpn. Basically its cna ma cma lpn rn. You can go to school for whatever you would like and do not have to have prior medical.
You do not need to be certified to be a CNA if you wish to go on to be a LPN. However, this will depend on the requiremenst that have been provided by the nursing school you are attending. Working as a CNA provides you with more experience.