Can I do diploma in Hospitality and Hotel Administration in Canada?

I can't understand your question, what you want to ask. If you want to know about how to get admission for any Diploma in Canada, then of course you can get admission. If you are class 10th and class 12th pass with excellent marks in English, then you can apply directly for any Diploma in college of

Yes, you can do post graduate Diploma in the same field you had done under graduation. Few colleges will give you graduate Diploma program also. You should know the stay back options in Canada. If you do one year program, you will be extended only 8 months visa. If you do two year program, then you