different sizes, small and large. it depends on local population and need of Muslims.
It's not a must to build only big mosques, it's also allowed to build simple mosques...because & simply the mosque is not in its size but in its spiritual value. But , most of the mosques are...
badshahi mosque
It is so big that it can accommodate 4 million praying Muslims. Refer to link below for more information.
yes there is