when a christian , or a jew or a muslim converts to another religion , most propabley he will practice the new religion, other wise why he convrted from the begining, jews were practicing their Judazim during his life , its a taboo in islam to harm any timple or church any where, there was no christianity in the area, and jews left for reasons documented in history, all mousques in the world are open to visitors from non-muslims , with few conditions, only the two mousques in madina and mecca ar not open for nonmulims, you can watch how crouded they are along the year, as they are not historical or tourism attraction,many historical mousques in the old islamic coutries are open for visitors, I took many non-mulim freinds there myself,one hint here, there is no christians or jews living in the two cities, they are oriented around the religious vistors only,
plz dont husitate to ask any thing else,
kind regards