You cannot take more than 19 units your first quarter of freshman year because you have to petition. I believe you need at least a 3.0 UC GPA for them to approve. Since you are an entering freshman, you won't have a UC GPA (unless you took some classes at a UC already in high school).
yes. class standing is irrelevant, it's what year you are. it's not even much of a worry anyway because anybody can actually take them; i took a fiat lux when i was a 2nd year and there was a girl in my class who was a 4th year. as far as i know, they become open to all class standings once all the 1st years have a chance to register for them.