Questions about Supplication and Dreams

[Nitro Zeus]

Assalamu alaikum,

I always dreamt to see what is the status of my grandfather in grave, because he died as Christian and buried in Christian graveyard in Bucharest, Romania. And I don't know if he received correctly the message of God or not, so I can know if I can ask God To grant him success and help on the Day of Judgment to my grandfather so I can see him in Paradise. Also, I want to ask God the same for the case of his dead parents and others before him. If I received the answer from God then so be it, I'll not ask Him this because I know asking God To grant Paradise for a disbeliever is forbidden in Islam. Also, I'd like to see whether or not my grandfather is punished in his grave or not, so I can give good news to my mother who's Christian so she can feel happy to hear that her father is alright and she doesn't need to worry about him and just to stay calm.

Also, I dreamt of seeing with my own eyes the life of grave and see what is in there just as my little journey so I can have an idea of how the life of grave looks like.

Also, I dreamt of asking God things about Paradise which are kept silent, because I have questions which I cannot find it in Sunnah and neither in Quran and some of my questions are strictly personal which I want to know from God Almighty and not from people.

My questions are:

1. Is it permissible in Islam if I supplicate for God To show me in true dreams?

2. How can I start having true dreams(I mean those type of dreams when you see at night the next day it comes reality)?

3. Is it permissible if I want to ask God for things related to Unseen?