The correct answers are As soon as I pressed the red button, I found myself in ancient Rome. and Before I spoke to the emperor, I had hidden my smartphone.

When talking about the past, time clauses must align with past tenses.

"until I have seen" is incorrect because it mixes past simple with present perfect. It should be "until I saw" or "until I had seen."

"After I hide" is incorrect because "hide" is present tense, but the main clause ("spoke") is in the past. It should be "After I hid" or "After I had hidden."