Dark Souls 2 Compatibility Question

Disconnecting the console from the internet is the only sure way to prevent player invasions in Dark Souls 2.

That said, there are many conditions for both being able to invade and being susceptible to invasions, so your friend shouldn't have to worry too much. In my 72 hours of playing the game, I've been invaded only 3 times, not counting the areas belonging to the PvP-covenants. Those are entirely optional.

Like the comments above mention, you can minimize invasions while online for about an hour by burning a human effigy at a bonfire. The item description for the human effigy mentions this effect:

A warm, soft, shadow-like effigy. Use this item to reverse Hollowing. It also weakens the links to other worlds, preventing invasions and most cooperation. Peer closely at an effigy, and one begins to perceive a human form, but whose form it takes depends on the person looking. #

The Way of Blue supposedly summons available members of the Blue Sentinels covenant to help the Way of Blue player being invaded. I don't believe it matters whether the Way of Blue player is hollow or not, but the Blue Sentinel must be human, wearing the ring and also not fighting a boss or near a boss gate. With all these conditions, I'm not surprised people have seen few protectors these first few weeks after the game is out. Only a portion of players elect to join the Blue Sentinels, and then they both have to sacrifice a ring slot and not lose their humanity to be able to help.

Since your comment mentions the original Dark Souls, I'll add that in that game you would never be invaded if hollow; only in human form. So you could easily play through the whole game without disconnecting your console and never be invaded.

In my experience, invasions have resulted some of the most nerve-wrecking and adrenaline-filled battles in the Souls series. They've also been some of the most memorable, so I recommend not trying to prevent them.

With all the different versions out there, the publisher made this quite confusing. If you have the DX9 version of the original game with the Season Pass, you can upgrade for 20$, without the Season Pass for 30$.

Scholar of the First Sin (SotFS) is basically a "complete edition" of the game. It includes the base game and all DLC. In addition to that, there will be a patch that adds things like new NPCs and re-balancing that is already included in the SotFS edition, but will be available as a patch for the original game as well.

The benefit of upgrading your DX9 to the DX11 version are improved graphics (obviously), and gameplay changes that are exclusive to the DX11, Xbox One and PS4 version. These include new placement of the enemies (e.g. Heide Knights actually being in Heide's Tower) and more online players in a single session. These changes will not exist in the DX9, Xbox 360 and PS3 versions.

The SotFS edition for DX9, Xbox 360 and PS3 is just the patched original game plus DLC, nothing more. Players of both versions will be playing on the same servers. Players of the DX11, PS4 and One versions will play on different servers, which means you can no longer play with people who have the DX9 version on PC with the new version. You will still keep the original version though.

Here is a table that details the different versions (found on videogamer.com):