For my country of citizenship, I do need tourist visa for Canada. However, all I need to do (for the sake of arranging my immigration status in USA) is leave USA and come back, so I will not even leave the terminal area in Canada, just fly back the same day to make a fresh re-entry in USA. Will I need a Canadian visa for this? Is there anything to stop my flying out to Canada, provided I do not leave the terminal area?
It is possible to do a visa entry without flying (to Canada). For example, wherever there is a bridge to Canada (Detroit, Buffalo, etc) you can go partway across the bridge, turn around, and come back through US immigration.
The trouble you will have with a flight to Canada is the airline will want to be sure you have the right to enter Canada first (especially since you require a visa to enter Canada). Without a visa, you probably won't get on the plane.
I’m not sure I fully understand your question and situation, but it sounds like you are staying in the United States with a valid visa (multiple entry visitor’s visa?) and must leave the USA briefly and then return in order to satisfy the requirements of your US visa regarding how long you can legally remain in the US on any one visit. Since you mentioned that your country of citizenship requires a Canadian visa for entry to Canada, and assuming that you are not a US citizen or US Green Card holder (based on what you said), you may need to have a valid Canadian visa even for a brief transit through Canada. Even if you are from a visa-exempt country, unless you have a valid Canadian visa or are a citizen of the USA, you will likely need an Electronic Travel Authorization (eTA) in order to visit or transit through Canada.
You can buy a same-day return ticket on Air Canada, Air Canada rouge, Jazz Air, Air Georgian, Sky Regional or WestJet, to Vancouver, Calgary or Toronto Pearson terminal 1, and bypass Canadian immigration altogether, because these airports have direct corridors to US preclearance.
In practice, you may have a hard time convincing the airline to let you board without a Canadian visa, as this technically wouldn't count as a connection, but a return trip.
Nevertheless, try asking any of the above airlines whilst explaining your situation, and remember, if any of them agree to transport you, they must put SSR TWOV in the PNR