Elections in each province are implemented through an organization maintained by the provincial parliament or legislature. Ontario's will serve as the example.
They assign the polling stations, print the ballots, set up polling booths, accept and vet volunteers to run the stations, and probably most importantly for this question, count the ballots.
Currently, Ontario uses paper ballots. These are hand counted. This begins as soon as the poll is closed. The details of this process are controlled by Elections Ontario. They are presumed to be kept honest by having the various political parties provide volunteers so that nothing is every done by only one party.
The details of the procedures are not in the constitution or similar documents for each province. The legislative body of each province sets their own detailed rules. Often these details will be determined by the officials in charge of entities like Elections Canada. There is a significant body of rules regarding things like specific forms of advertising, who can register to vote, how to register, etc. You can find them on the web site.
The ballots are counted by hand as soon as the poll closes. The results are reported through Elections Ontario, and then passed to the political party officials and the media. During an election, the web site will sometimes display the partial results on a riding-by-riding basis, or even a polling-station-by-polling-station bases.
If you are interested in such things it can be interesting to watch these results as they become available. During the most recent provincial election in Ontario, my own riding was quite close and was not called until after I grew tired and went to bed. The final results were that the winner had a margin of 89 votes, or 0.26%.
If the election results are sufficiently decisive that nobody asks for a recount then the losers will usually concede. Often this shakes out within a few hours of the poll closing. If the results are close then a recount may be requested. This nearly always finishes within a small number of days, say 3 or 4. But sometimes it results in more delay and rarely even law suits.
Usually the results are known by the next morning at the latest. For province-wide elections the results for the provincial government are nearly always known the next morning.
When a riding is decided and no party is contesting the results, then Elections Canada will eventually decide it is time to destroy the ballots. This officially closes the election in that riding.
As to the second part of your question, there are no formal rules for that. Different politicians will have different ideas. At one extreme, some will have detailed policy documents published well before the election. At the other, it may be many months before any details of policies are announced.