What is the meaning of "precautionarily" in the context of not engaging in supererogatory prayers for someone who has missed obligatory prayers, and is it permissible for someone who has missed obligatory prayers to perform supererogatory prayers while including another intention, such as the prayer of Istikhara, the prayer of need, or the two rak'ahs before marriage?

We have mentioned in previous fatwas the scholarly opinions regarding the ruling on performing supererogatory prayers for someone who has missed obligatory prayers. If you adopt the view of those who disliked absolute supererogatory prayers but permitted other types, such as the Hanafis, then there is no harm upon you. However, if you desire caution, then abandon all supererogatory prayers and focus on making up the missed ones, in consideration of the opinion of those who prohibited it in this case, and observing differing opinions is recommended. If someone who has missed obligatory prayers performs supererogatory prayers, imitating those who permitted it, there is no impediment to sharing the intention between acts of worship where such sharing is permissible. And if the person performing supererogatory prayers intends to share the intention of more than one act of worship with their prayer, there is no harm in following someone who does not have that same intention.