My understanding of "till":
I use "till" at least as much as "until"--even in formal writing. So, when I saw ## 3, 4, and 5, it made me wonder whether my practice is faulty.
Of the nine online dictionaries I consulted, only one (Macmillan Dictionary) suggests that "until" is more formal than "till."
The other eight dictionaries (including the popular Merriam-Webster; and Webster‘s New World College Dictionary) seem to treat both words with equal dignity and put them on equal footing.
(I do consider ‘til--the contraction of “until”--to be informal, but ‘til is not the same word as “till.”)
American Heritage Dictionary of the English Language
Middle English, from Old English til, from Old Norse
Till and until are generally interchangeable in both writing and speech, though as the first word in a sentence until is usually preferred: Until you get that paper written, don't even think about going to the movies.· Till is actually the older word, with until having been formed by the addition to it of the prefix un-, meaning "up to." In the 18th century the spelling 'till became fashionable, as if till were a shortened form of until. Although 'till is now nonstandard, 'til is sometimes used in this way and is considered acceptable, though it is etymologically incorrect.
The noun till means the same as "cash register." When you work at the store long enough, they'll let you operate the till. When you pay taxes to your town, they go into the local till, or government fund, for community improvements. Till is also used as a verb, meaning to work the land, to get it ready for planting and harvesting. Till can also be used to mean "until," which makes things a bit confusing. So, technically, you could have a sentence like: Don't touch the till till you take the customer's money. (Emphasis added.)
Till means until.
An example of till is someone saying they aren't able to leave work before they finish a project, till they finish a project.