The easy way to disable apache proxy functions is to comment out the lines that load mod_proxy, mod_proxy_connect, mod_proxy_ftp, and mod_proxy_http. Here's an extract from my apache.conf file where I disabled proxy functions:-

#LoadModule proxy_module modules/mod_proxy.so
#LoadModule proxy_connect_module modules/mod_proxy_connect.so
#LoadModule proxy_ftp_module modules/mod_proxy_ftp.so
#LoadModule proxy_http_module modules/mod_proxy_http.so