Does "إن" (if) followed by "ف" (then) in the noble verse, "And if you are prevented, then [offer] what can be obtained of sacrificial animals," and "And if you fear that you will not deal justly with the orphan girls, then...", indicate the determination of specific conditions?

The two verses comprise a condition and its answer. In the first verse, absolution from Hajj or Umrah is permitted on condition of being prevented (from completing the rites), and it is understood from this that absolution is forbidden when there is no such prevention. In the second verse, marriage to an orphan girl is forbidden when there is fear of not being just towards her, and it is permitted when there is certainty of being just.