Definitely not! It will be difficult and stressful at times but you can definitely do it! I am at university and still compete and work with young horses, it's all about how you manage your time. If you are starting out I would advise you maybe to get a job at a stables one or two days this will give you an insight into the life of eventing. One thing I find very helpful is to chose a day or two (Saturday&Sunday) and make them your full horsey days. I make sure all my studying and work is finished for these days so my full focus is on my horses. Hope this helps and good luck 👍🏻
I don't think so, I usually go up to see my horse on the weekends and after school. I am in high school so I would be different if your in college but I see zero problems with it you don't have your own horse!
If you feel you are deciding to make this your true future and career. It's not necessary to give up school for equestrianism, but my advice would be to stay in school. If you were to get injured and couldn't ride anymore, it's always good to have something to fall back on. :)