I am in the united States but I would be very surprised that a banking institution would not credit/charge interest on weekend days. Trying to calculate interest would be more complex if they also had account for weekends and holidays.
On this site you will see questions about calculating interest. Some want to know if the bank uses the actual number of days in the month, or just always uses 30. I know my credit union knows the number of days in the month.
The answer for checking and savings accounts should be the same. If the account earns interest it will also earn interest on the weekends.
The third question about timing is slightly more complex. If you go onto the website and transfer the funds on a Saturday when does the money leave your account. Only your bank can answer that question. But the concept is correct. If you can wait until Monday you can earn a little more money.
That extra float is why in the early 1990's I started paying some large bills by credit card. My local government allowed people to pay their property tax by credit card for no fee. I could delay the money leaving the bank for 6 weeks using the float of the credit card billing cycle. Plus I earned 1% back from the credit card. Now my county charges 2.5% for the credit card transaction so I don't use the card for that transaction.