You can apply for as many visas as you want simultaneously. Only remember the intention. Some visas are settlement visas while others are not.
Look at his link and see the reasons why this person got rejected for a visit visa. Student visa is also non settlement.
http://www.canadavisa.com/canada-immigration-discussion-board/my-gcms-notes-for-visitor-visa-applicationneed-suggestions-please-t480602.0.html