sorry guys but your answers are so complicated.
he saied that he can not applying online for extension of visa.
just he needs to know is there anyone who has a visitor multiple visa and passing the border of canada to usa and then when he comes back to Canada, his visa being to be extended or not.
thats it thats all.
because multiple visa means that you can going out of the country ad then you can go back again to canda for next 6 month !
so...
he can go out of the country and go back again to canada for next 6 month.
its multiple visa and its not single.
in this way his visa should be going to be extended.
Sure a multiple entry visa means just that that an holder can travel to Canada multiple times for the validity of a visa. As with any visa it does not guarantee entry to Canada that is at the discretion of the CBSA officer at the border and they will be assessed afresh as visitor for purpose of visit, finance for a visit and so on. Worst case they could be given a specific record to enter but leave in a couple of weeks or even worse be refused entry which would be extreme and maybe unlikely..
So if someone has already been in Canada for 6 months as a visitor then it is usually expected that they go home for a period of time say 6 months before attempting to return to Canada else it could be considered they are trying to live in Canada and even be suspected of working illegally to support themselves, not saying that is the case here.
This is why there is the extend stay as visitor process, to apply from within Canada to extend a visit stay without leaving the country. Saying someone cannot apply online or even if available on paper would not be an acceptable excuse given the process is not exactly complicated.
So sure someone can cross into the US assuming they have a US visa , stay for a day or so and try crossing back.Not sure whether flagpoling would reduce the odds of approval or not but guess that could be considered.
If CBSA accept their reasons for coming back so soon as a genuine tourist/visitor then fine but this will likely only work the once so beyond that will need to return home for probably a similar period to the time spent in Canada.
Ultimately though of course all anyone can do here is to speculate, the decision is with CBSA but using the extending stay as a visitor process/form would be 100 percent easier to achieve especially as once application is in process the applicant is on implied status pending a decision plus no need to go anywhere or face CSBA.