In asking this question, the questioner has already assumed the existence of gravity. By definition, God created everything. Hence, God created gravity. Since God can create gravity, he can certainly make it disappear. So God can carry any stone. Put another way, this question could become: if God were to have an arm wrestling match between his right arm and left arm, which arm would win? Both arms belong to God. This is not a contest; there is no winning or losing. Therefore this is a stupid question.