When you ask "whether you can say them", do you want to know how natural these are in everyday conversation, or are you just interested in whether they are correct English? For example, "We believe her to be innocent" is perfectly good English, but in conversation most people would be much more likely to say "We think she's innocent". Similarly, in conversation, "we're" would almost always be used in #19, and "I'd" in #2, even though the uncontracted forms are, again, perfectly good English.
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