A person prays in a certain spot within the rows of the mosque, and gets angry if someone else prayed at his spot. What is the ruling on this behavior?
All Perfect Praise be to Allah The Lord of The Worlds and may His Peace and blessings be upon our Prophet Muhammad and upon all of his family and companions Prophet Mohammad (PBUH) make it prohibited for a Muslim from having/taking a certain spot in the mosque when performing prayers if they arrived and find it occupied, furthermore; it is the religious duty on others (praying people) to offer a piece of advice to alert the ones who don't know, that whoever reaches a spot first at the mosque having a priority/privilege upon others in that spot. And Allah Knows Best.
Can someone who begins a voluntary fast break it?
It is preferable for someone who begins an act of worship not to break it.
Allah the Exalted has said {what means}: "and let not your [good] deeds come to nought!" [Muhammad/33].
However, if a person starts a voluntary fast (nafl) and needs to break it, they are going against what is preferable, but there is no sin upon them.
For some time I have been searching for a guiding shaykh to teach me the spiritual path (*sulūk*) and the Islamic sciences, but I have not found one. What should I do?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
There is abundant good in this Ummah, and the scholars who guide and nurture are never cut off. The student of knowledge should strive in seeking them out, ask diligently after them, and draw from their learning.
As for one who cannot find a guiding and nurturing shaykh, he should send abundant prayers and peace upon our master the Prophet (peace and blessings be upon him), while keeping constantly to dhikr and worship and abstaining from the forbidden. For that will bring him to his goal in traveling toward Allah the Exalted. Imam Muḥammad al-Sanūsī (may Allah have mercy on him) said: “I have seen it said by some of the imams of Sufism that whoever lacks shaykhs of spiritual training (shuyūkh al-tarbiyah) should increase his invocation of blessings upon the Prophet (peace and blessings be upon him), for by it he will reach his goal.”
The scholar Aḥmad Zarrūq al-Mālikī (may Allah have mercy on him) said in Qawāʿid al-Taṣawwuf (p. 86), rule no. 114: “Dhikr is the decree of sainthood (manshūr al-wilāyah). Whoever is given dhikr has been given the decree. Our shaykh Abū al-ʿAbbās al-Ḥaḍramī (may Allah be pleased with him) said: ‘Keep constantly to dhikr and abundant blessings upon the Messenger of Allah (peace and blessings be upon him), for it is a ladder, an ascent, and a path to Allah the Exalted when the seeker does not meet a guiding shaykh.’” And Allah Almighty knows best.
Should nail polish be removed before making ablution?
Yes, it should be removed because it prevents water from reaching the nails.