The original sentence is
Er geht um sieben Uhr zur Arbeit.
It is okay to say
Um sieben Uhr geht er zur Arbeit.
However, how about
Zur Arbeit geht er um sieben Uhr?
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Sign up to join this communityIn general, word order in German is flexible: You can move around nearly every part of a sentence except the verbs.
However, deviating from the natural order will emphasize parts of the sentence. The more you deviate, the stronger the emphasis.
Er geht um sieben Uhr zur Arbeit.
is neutral.
Um sieben Uhr geht er zur Arbeit.
emphasizes the time, but not extraordinarily so.
Zur Arbeit geht er um sieben Uhr.
emphasizes "zur Arbeit" very strongly: It is (really) work he goes to at seven o'clock.
And as you can see, English has a similar construction using "it is X that/who/...". For the same reason, the literal translation of this construction "Es ist X der/die/das ..." is rarely used, that's a common mistake by English native speakers.
Your last one is also correct. This question is put by someone who is unsure whether the time is seven.
Zur Arbeit geht er um sieben Uhr? Und nicht um acht?