I haven't heard anything about people spamming the log in button, but I'll be honest you can spend hours clicking the link to get into mugsi, then into solar. I would recommend trying logging into Mugsi before the hour that solar opens that way you've already by passed one obstacle lol.
It's really all up to luck if you get your course elective, don't be discouraged if you don't get a spot by the time school begins, keep checking in on solar, sometimes people randomly drop the course, especially during the first 2 weeks of school.
As for residences, you are correct, first years do not get a guaranteed spot unless they have a certain admission average. This past year it was a 79% admission average, and this coming year we're expecting at about 80%. You will be notified if you have a guaranteed spot on you acceptance letter. And if you don't manage to reach that admission average, you'll be placed on a waiting list, and you'll be ranked according to your admission average. 80% of residence space is reserved for first years, you do get to choose 5 preferences when you fill our your residence application form as to what style you would like. Your name is placed into a lottery system, when your name is picked, it will look at your first preference, if it's still available at the time your are chosen, you'll get it, but if not the computer will give you your next available preference
. To get a guaranteed first preference, you need an admission average of 95% or higher!You'll know your room assignment and roommate if you have one by end of July usually.
Best of luck!