As far as the hull design yes it is the same of the Speedster for this year, both are 14'.
You could definitely do a powerturn on this boat, pretty easy to do 180's and 360's. It is possible to "submarine" this boat too, but I would recommend search the forums on same dangers of doing this. Search for "sub-doo", if you have problems locating the post then let me know and I will dig them up.
The smaller the hull the rougher the ride is going to be, with it only being 14' you are definitely going to feel the "chop"....this is totally opinion based on how much is too much for you so I would suggest test driving the boat to see if you like how it rides. It shouldn't use too much fuel, it does burn both gas and oil so it will smoke a bit but this is completely normal.
Yes it will be able to ride waves, you should also be able to jump the waves and get this whole boat out of the water!
If the seller doesn't list one coming with the boat then you will have to buy an aftermarket bimini top, there many places where you can find one of these for this boat.
I am not sure about ski pylons being available for this boat, but I believe there are some wakeboard towers available for this boat. You could try Monster Tower, http://www.monstertower.com/, or Joystick Pylons, http://www.joystickpylons.com/.
Like I mentioned above test drive the boat first, check the boat for any leaks especially in the engine compartment. Inspect the hull thoroughly for any damage.
The seller just told me that the engine starts perfectly, but when giving some speed, the engine diers out?
What could this be, he says he has changed many parts in ther engine,