People used to say "yesterday" as "yester-day" in the past.
It is correct to say "used to do".
I used to go to the movies.
I'd say they used their fingers
In French, "ciao" can be used as a casual way to say goodbye, similar to how it is used in Italian. It is not a formal way to say goodbye in French.
innumeration could be used
If you mean "used to," the imperfect auxiliary, then the main rules are: 1) Used to is always in the form of the past tense "used" and 2) It never takes its own auxiliary. We may say This used to be fun, didn't it? But we do NOT say Didn't this use to be fun?
Calcium, Lime and Rust which is used for the home... most places say not to use it
The plugin license will say if it can be used for commercial use.
Depends on how you want to use either of them, usually though, aloud is used.
A person who has something has it right now. They could say, "I have this." But if they give it to someone else, they no longer have it. They would not be able to say they have it. They would say, "I had it." Meaning they used to have it. 'Have' is present-tense, whereas 'had' refers to something you used to have, and is past-tense.
DoD may use them; if they are used, they only have limited pecuniary liability.