Are the unavailability of water or a place to pray in the mosque, or the inability to determine the direction of the Qibla, considered compelling reasons for not performing the Maghrib prayer on time? And is it permissible to perform Tayammum in the absence of water, or to wipe over a wall if no dust is available?

It is not permissible to perform tayammum (dry ablution) when water is available and one is able to use it. If water is not found except by asking for it, then it must be sought from people. It is not permissible to delay the prayer beyond its prescribed time under the pretext that there is no space in the mosque, for prayer is permissible in any pure place. If there is no space except on the pavement, then one should pray on it. As for the excuse of not knowing the Qibla (direction of prayer), one can seek help from someone who can guide them or use electronic devices. If that is not possible, then make an effort (ijtihad), and your prayer will be valid. One must preserve the prayer at its prescribed time, as it is among the priorities.