I have some questions about the PSN on PS4 that I would like to get sorted out. :)

1. My PS2 and PS3 games that I have bought for my PS3 from the PS Store, will I be able to play them on the PS4? Today or in the future.
2. Will I be able to buy games from the UK and US PS Store like on the PS3 or just the HK? (multiple accounts thing)
3. Will my friendslist, trophies and stuff that I have collected on the PS3 remain when I sign in on the PS4, or will they not be shown anymore?
4. Will there be released PS2 and PS3 games in the PS Store for PS4?
5. Any other useful information to know? Like what is new on the PSN that is not on the PS3.

1. Nope right now, in future? Gaikai for PS3 games?

2. Same as on PS3.

3. Everything will be there.

4. Gaikai for PS3 games. 

5. Your friends list will expand to 2000 people up from 100 on PS3.

This got me wondering, if you have over 100 friends on PS4, what happens when you log in to PSN via PS3?

1. Flow, Flower and Soundshapes are free downloads on ps4 if you own the ps3 versions. They're probably an exception though, I doubt it will be standard policy for all first party titles.
2. Probably.
3. Evrything is there and it now shows the rarity of each trophy. Synching only takes a couple of seconds (it was taking 30 to 60 sec for me on ps3) during which you can already browse the list.
4. Don't know.
5. Live streams, automatic game updates, background downloading, party chat, multiple user logins, ps+ mandatory for online multiplayer.

You can send messages between a ps3 and ps4 system, however screenshots from a ps4 do not arrive on a ps3, they do arrive on a vita. Messages sent to you arrive on both systems. (Not whichever one you turn on first like it was if you happened to own 2 ps3s)
If you're using a ps3 and ps4 at the same time, another friend's ps3 will show what you are playing on the ps3, while a friend's vita will show what you are doing on the ps4.

This is from PS blog.

The PS3 system will continue to support up to 100 friends at one time. If you build a friend list bigger than 100 on PS4, network servers will automatically filter your friend’s list when you play on a PS3 system. Additionally, you will be able to set and lock a pre-determined friends list to be used while you play on the PS3 system if you wish. Support for the ability to display all of your friends in most applications and games is planned, however, some titles will be limited to the current 100 Friends limit.

Why on earth would i need 2000 spots ._.

Gaikai was new to me. What exactly is this?

I read about it on their own website under the Q/A section, and it's a cloud service that will let me stream games, that I understood. But what exactly does this mean then.

The whole game will be streamed(nothing downloaded) and I will have to rely on my internet connection for the game to be stable? Probably yes.
And will my purchases on Gaikai and PS Store be the same, if I own it in PS Store I also own it in Gaikai? Probably no.

Because I would like to buy ICO/SotC HD on PS3, but if I can't play it on my PS4 and have to buy it again(if they even release it) in the PS Store or on Gaikai, then I would rather wait for it to be released for the PS4. Or else I might end up buying the same game two times.

Playstation Home on PS3? They have Playstation Mansion on PS4. True story.

With Gaikai the game is run by their servers (not sure how big their game catalogue will be .. I doubt they are able to provide every PS3 compatible game that way) and you receive a video stream, while your console sends back your controller inputs, so it's very reliant on your connection.

Unfortunately they haven't released any pricing details, but while I doubt they make you pay twice for the games you have in your library I think Gaikai might need another monthly/yearly subscription on top of PS+. And right now the service is only confirmed to release in the US (in 2014) ..

So, I guess if you want to play those PS3/2 games you better keep the PS3 around for now :/.

This kind of sucks for me, because where I live at the moment the internet speed is heavily slowed down during the late hours of the day because of so many people using it. And I normally only play during that time. I often do updates and stuff during the night when I sleep. Bummer. :(

Yeah I think so too, keep the PS3 for a while. And I guess if ICO-SotC HD would come to the PS4 it won't be this or next year. More likely in 2015 or so.

Thanks for the info!