Is it permissible to pray Dhuhr in the university mosque after the Adhan and before the Iqamah, if lectures begin at 12 o'clock, and is it permissible to pray it in congregation when circumstances prevent delaying for the lecture?

If the mosque does not have a permanent Imam, it is permissible to pray individually after the time for prayer has begun if there is a valid excuse for not joining the congregation, but it is better to pray in congregation. If the mosque has a permanent Imam, it is preferable to seek his permission, but the prayer is valid even if performed without it, especially if there is a valid excuse.