A simple question, trying to say, let's have a lesson from 4 to 5 -- want to make sure that "to" is indeed 到.
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到 is OK. You could also use 至. 到 is more colloquial. In many cases they are interchangeable, for example: 从古到今/从古至今（from ancient times to the present）, 直到此刻/直至此刻（up to now）. But you could only say 自始至终（from the beginning to the end），从这到那（from here to there） because 自始至终 and 从这到那 are kinda like set phrases.
yes, you are right.
The general meaning of "到" in Chinese is the same as "to" in "from...to", and also it has the meaning of arrival.