The title asks it all. Is porn allowed in Islam?
No it is not.
There are tons of quranic verses and hadith that describe about the ethical behaviour and clearly state that immodesty/unabashedness is a big sin and one must control not to do it.
To give a small but a very heavy reference is Surah An-Nur 30,31
Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do.
And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their headcovers over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.
Please read this link for a better explanation of this ayah.
So, bottomline, islam talks about modesty and clearly pornography is not allowed in Islam.
Of course it is not.
There are several reasons why the Muslims were visiting porn sites
Delayed age of marriage, and by virtue of the customs in Islamic countries Prevent non-legitimate relations, They visit those sites to compensate
No, Please check out this verse In surat "Al-Israa":
وَلَا تَقْرَبُوا الزِّنَا ۖ إِنَّهُ كَانَ فَاحِشَةً وَسَاءَ سَبِيلًا
Translation: "(32) Nor come nigh to adultery: for it is a shameful (deed) and an evil, opening the road (to other evils)."
No, it is common sense in Islam that watching porn is Haram. The only naked body allowed to be seen is the one of your spouse.