Yes, you can visit Canada if you have a visa, though you will have to get through immigration when you land. It is possible to be denied entry if you don't have a good reason for coming, or CBSA suspects that you aren't a real tourist/visitor.
No, you cannot "convert" your visa into a student or work visa. It is possible under some circumstances to apply for a brand new study permit or work permit while you are in Canada, but that has nothing to do with your current visa. It's just like applying from outside Canada - being here gives you no special benefits.