Windows 8 Start Screen: Show programs in order of most frequently used

No, you can't. There is no inbuilt option and no app available yet which will let you do the purpose on the Start Screen. You can obviously get start menu replacements for Windows 8 which have the sort by most frequently used feature.

To create groups, check out this link.

The tiles stay still by design - and you can organise them into groups which can be moved as a whole (when zoomed out) - simply drag onto the bar between two groups, or to the right of the right most group to create a new group.

You could get back the old start menu which would have this behavior. You can do this by installing a 3rd party app such as:

• ViStart
• Classic Shell
• Pokki
• StartMenu7
• Start8