Feel free to inform me in whatever way you'd like if these have already been requested, or are already in the works, or are already in a 4.7 beta, but these are three things that I was used to having when I used virtual desktops as makeshift activities but now don't have with actual activities. It'd be nice to have them back.

#1: Does Plasma use any sort of system to sort activities? They don't see to be in the order I created them, alphabetical order, reverse alphabetical order, or any other ordering system I know of. Either way, is there a way to sort the ordering activities appear in (preferably arbitrarily), as this affects the order they appear in the Activity Bar, the order they're switched to with Meta+Tab, and in the right-click menu for application title bars.

#2: Is it possible to force applications to appear only on specific activities, or on all activities consistently? This seems to me like it would be fundamental to activities but I've found no way of doing it.

If I launch Iceweasel from the File Browsing activity, it appears there rather than on Web Browsing, where I always want it to be. I'd like to be able to lock Iceweasel to that specific activity, so it only launches there, regardless of where I launch it from.

Also if I have GIMP open with a file already open and open a second from File Browsing rather than Image Editing (where GIMP lives) the child window appears on File Browsing rather than Image Editing, and I would prefer that child windows stay with the parent window.

Finally, applications like Sonata and Choqok (which I associate with no specific activity, they live in the system tray) keep getting locked to the activity I first launch the windows for them on (sometimes even switching me to another activity when I open the windows, which is just plain annoying). I want Plasma to know that these applications should always be associated with all activities.

#3: Virtual desktops allowed me to bind key combinations to specific desktops (I generally bound Ctrl+F1-F8 to mine), but I can't see any way to do with activities. I can select an arbitrary activity with Meta+Q and the mouse, but mixing keyboard and mouse for this is awkward and slow. I can cycle with Meta+Tab, but this is also slow and I keep overshooting the activity I'm aiming for when rapidly cycling. An extra Activity Bar would also be an option, if I didn't keep my applications maximized all the time, which is why I used key combinations in the first place. So being able to associate specific activities with specific key combinations would make things a hell of a lot easier.

On #2, I don't think that was the intent with activities. The intention was that you have e.g. a development activity and a leisure activity, and a photo editing activity, and you could have a web browser and a file browser open on all three with different pages open (rather than having a file browsing and a web browsing activity, because you don't get on your computer to browse files, you get on your computer to play games or to work on some project or to chat with your friends). When you launch an application in a certain activity it is assumed that you intend for it to open on the current activity so that you can use it for whatever you are currently doing on that activity (I'm in my development activity and I open gimp so I can edit the splash image for the application I'm working on). If you just want spaces to put different applications' windows, that is why virtual desktops are still there, and you can set up rules to force certain applications to specific virtual desktops.

As for #1 and #3, I don't think either of those is currently possible. You might search the forums (esp. the Brainstorm forum) to see if someone has already asked for the feature, but if you don't find any results go ahead and post the ideas to the Brainstorm forum (as separate threads). I personally like both of those ideas. Of course you can always post idea #2 to the brainstorm forum as well and get more specific feed-back, and see what the general consensus is on the topic.

#1 the order will be based on the most used activities (highest rated)

#2 one of the planned things, not implemented yet (it is a junior job, so anyone willing is more than welcome to do it)

#3 i thought it was implemented, or somebody just planned to do it

AS for #3 you can do it with a qdbus trick. You should create a custom shortcut via the Shortcuts and Gestures. İt should be Global Shortcut and Command/URL. Assign your desired keyboard combo in trigger part. The command is this:
qdbus org.kde.kactivitymanagerd /ActivityManager SetCurrentActivity ${activityId}

To obtain your activity IDs you can issue this command:
qdbus org.kde.kactivitymanagerd /ActivityManager ListActivities

The activity IDs are listed without names. To obtain a name:
qdbus org.kde.kactivitymanagerd /ActivityManager ActivityName ${activityId}

I also use a panel at the top which contains an activity bar. This way a maximized window won't overlap your activity bar.