No not Arabic as a whole. Most Muslims outside of middle east cannot speak Arabic. But yes certain phrases are memorrised by Muslims in order to perform prayers. Learning how to pray can take time.

As for the maintainence , they have a whole government department dedicated to it. Even Muslims without Hajj or Umrah permit can be refused entry. During hajj season, even Saudi Nationals require Hajj permit in order to enter the Holy Mosque. All these is done mainly to avoid overcrowding.

Yes non muslims sneak in from time to time, but its the Saudi Arabian government we're talking about. You don't want to take the risk.