Yes. It's not necessary to treat every yeast infection when you're pregnant. However, it it's really bugging you then it can be treated with topicals like vagisil. If that doesn't work, then your doc can prescribe something stronger to knock it out.
Yes, but . . . Yes, but why would you want to? Vagisil is, at best, a temporary moisturizer that treats symptoms, not causes, of vaginal dryness and in the process may disrupt normal vaginal acidity, leading to other problems. If you're having a problem that leads to your use of vagisil, see your obgyn to determine the cause and treat that. By the way, if it's lubrication, pregnancy often solves that problem.