PHP 5.5 vs 5.6

First time installing grav using the grav-admin donwloaded on a shared hosting and it was on PHP 5.6 - the error page shows up and says that using 5.6 is "too advance?"

and when switching to PHP 5.5 a new error comes up and says
"The requested URL /grav/admin was not found on this server."

searching the folders, one cannot find "admin" folder

Well the error saying PHP 5.6 is too advanced, is quite strange as Grav supports PHP 7 from a very long time, too. Do you have a screenshot of that error? Is this the latest Grav?

For the 404 error, make sure you copied .htaccess to your server too

Grav has a minimum requirement of PHP 5.5. PHP 5.6, 7.0, and even 7.1beta work fine with Grav also.

thanks flaviocopes, didn't copy the .htaccess. had just uploaded the zip file and unzipped it on the shared hosting.

changed php version to 7.0 and the page that shows error does appear but instead there is a 404 looking for a non existent folder - ../grav/admin

Rewrite issue I would guess. Check the troubleshooting docs.