No it is not backwards compatiable. WAMP is not a program as such.. but the components are not usually fully compatiable.
It really depends on the versions you have now. if they are very old, they may have depreciated code.
As for writing over the websites, The databases are stored in the current MYSQL, and if you installed a new version , it will be blank. so thats would really work, you will need to export the DB into SQL format and reimport them after.
if you want to get teamviewer ill help you so thast you dont risk losing any data.
Steven Martin
stevenmartin99@gmail.comstevenmartin99@hotmail.comPampServer.com - [
pampserver.com]