First two questions are easy, the rest - not so easy.
you can get married in Canada on pretty much any VISA - i know of several examples.
If you want to work in Canada, you will need an employment visa, which is much harder to get than a tourist visa - as your employer will have to show they NEED you, and no Canadian wants the job. You also need to enter Canada on this visa, you can't change once you are here without leaving the country (24h in US will work, but to do that you will need a US visa)
Number 3 - once married everything isn't alright, you will still need to apply for a PR to permanently stay in Canada, and this can be a very lengthy process. You can remain in Canada on the visa you arrived on, but you will need to leave should the visa run out and your PR status not yet granted. Where you go will depend on your ability to get a VISA elsewhere.
In Canada you can get married without your parents. Your marriage in Canada however should be legal in both your countries. In
Bangladesh you can get married without your parents permission, but it's uncommon.
how do you prove that you will return to Bangladesh? good question! my personal opinion is that you show a HUGE bank balance. It's also my personal opinion that this is a load of rubbish, and what Canada really cares about is that you will bring to Canada a boat load of cash, and not end up on welfare (social services), however i do joke with my wife that the simplest way to get into Canada would be to claim refugee status, maybe she is being persecuted in Bangladesh because she is a bangladeshi married to a white bedeshi christian canadian, and she is being persecuted as a result.
Now - more seriously. You say you were not born in Bangladesh. If you were born in Australia, do you not have the right to Australian citizenship, that will make getting a tourist visa immensely simpler, as Canada is prejudiced against bangladeshi's and it's far far more difficult for a Bangladeshi to get a visa than an Australian. In fact, the Swiss ambassador in Dhaka suggested that we should go to switzerland, get citizenship there, then both of us travel to Canada on an EU passport - it would take less than 3 years. I could get an EU passport through my father who was born in Scottland, and actually this is a very tempting idea! It's sad that the simplest way for my wife and i to visit Canada is to give up my Canadian citizenship, but there you have it.
Of course, in your case you wish to settle in Canada, ultimately this will require you get PR. That's not going to be a fast process for any nationality, so you should start asap. One thing that my wife and I did do was get legally married at the earliest convenience, This allowed us to start processing legal documents (namely her passport) so that when we were married as per our wish, we would be able to go on our honeymoon outside Bangladesh. We had also thought to apply for her Canadian Tourist visa before being guaranteed a refusal.
so it boils down to two things, Do you have a lot of money? (don't answer that, just think about it) and can you show that you are not going to be living on Welfare (social services) if you go to Canada. Your education (where, major study) your work experience, your English ability (obviously pretty good), property you own, etc. so on and so forth. Canada uses a point system for immigration:
http://www.cic.gc.ca/english/immigrate/ ... /index.asp
http://www.cic.gc.ca/ENGLISH/informatio ... s/EG74.asp
http://www.workpermit.com/canada/points_calculator.htm
http://www.canada-city.ca/canada-immigr ... ssageid=33
(only the first two links are from the official government website - they might not be the right guide for you, but i hope it's a good starting place - the gc.ca website is a tangled mess)
One other thing to consider is to apply for immigration to Canada on your own. As sponsorship once you are married is limited to your husband, if he isn't going to be any help, you might wish to immigrate on your own merit or with sponsorship from an employer, another relative, his parents or whatever (i'm not really sure what, but that's the feeling i get). As you can see - the worksheet is for employment based immigration allocates most of the points for your ability, not your accompanying spouse. When you try for PR based as a spouse, your application can rely totally (if he fails to qualify as a sponsor) or largely (if he is a borderline sponsor) on your spouse, and not your merit at all.
regardless, as you are not only in Australia, but have never lived in Bangladesh, you will likely find that immigration will be easier for you, how much easier i can't say. First things to find out are, how much easier would it be for you if you held a passport (citizenship) from the country where you are born. Canada not only wants to know what your citizenship is, but your birth place) so that will make a difference even if you don't have citizenship. Canada and Bangladesh both allow for dual citizenship.
I don't know if you can apply for immigration to Canada from the Australian High commission, what i do know is that we can't apply from the Delhi High commission, which is a lot closer and easier for us to go to. We have been told that we can only apply from Singapore. However, if you were born in
Australia - that might have some bearing on where you can apply from. Also - keep in mind that the people in Australia are going to be issuing you your visa, and they probably aren't so accustomed to refusing VISA's to bangladeshi's as the office here in Dhaka is.
I would strongly advice you to go there or if it's too far, phone them, and speak to someone there to find out what they can/will do for you.
nationalism = boys with guns.
one hope, one world, one nation.