I went and spoke to my local Reserves while I'm at uni. Firstly, there is a chance you can be deployed, but if you request to defer it as you're studying, they will accept your request and not make you go, in fact the lad at the reserves said they pretty much ask if people want to go. With your second question, as long as you get the required days which is 27 days a year (this includes the 15 day annual camp) there should not be a problem. Thirdly, you will have a training night every week, which usually lasts around two hours, and you will also usually do one weekend every month.