Do the dead hear? While they are in their graves, do they see just as those who are alive do? Will they know one another on the Day of Resurrection? What is the ruling on making out with young women without having intercourse?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

For information about whether or not the dead hear what the living say, as well as whether the dead — while in their graves — see the actions of the living, then these are matters of the Unseen about which we have no authentic evidence.

The answer to your third question is definitely yes. The dead will know one another on the Day of Resurrection. When Allaah The Almighty resurrects the dead on the Day of Resurrection, there will be three types of people: non-Muslims, hypocrites, and Muslims. The Sharee‘ah texts indicate that people will know one another on the Day of Resurrection. The dignitaries who used to be followed in life will dissociate themselves from their followers. Allaah The Almighty Says (what means): {[And they should consider that] when those who have been followed disassociate themselves from those who followed [them], and they [all] see the punishment, and cut off from them are the ties [of relationship].} [Quran 2:166]

Allaah The Almighty Says (what means): {Close friends, that Day, will be enemies to each other, except for the righteous.} [Quran 43:67]

People will recognize the Prophets, may Allaah exalt their mention. They will ask them to ask Allaah The Almighty to rid them of the horrors of that Day. They will go to the Messenger of Allaah, sallallaahu ‘alayhi wa sallam , and he will intercede, asking Allaah The Almighty to have mercy upon them.

This is known as the Major Intercession and the Praiseworthy Station that Allaah The Almighty has made exclusive for the Prophet, sallallaahu ‘alayhi wa sallam.

Moreover, Sharee‘ah texts indicate that the people in Hell will know and rebuke one another, and that those in Paradise will visit one another and will receive bounties. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said that a man who used to advise people in this world to observe religious duties but failed to do them himself will be thrown into Hell on the Day of Resurrection. His intestines will come out of his body (due to the force he will enter with) and he will move around them in circles. Those who recognize him will ask him why he is in Hell. He will tell them that he used to advise people to do good acts and refrain from doing bad ones, but he did not do good acts and did bad acts. [Al-Bukhari]

The people of Paradise will meet one another in the market of Paradise every Friday. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said that there would be a market in Paradise to which the dwellers of Paradise would go every Friday. [Muslim]

There are many other relevant Hadeeths on this particular matter. 

In answer to your final question, such acts with women is absolutely impermissible.

Allaah Knows best.