Why the edges aren't equal and have stringing?

I use Prusa i3, and this is ABS printed part with 225/90 degrees temperature. Why this happened?

Top surfaces have gaps in that indicates under extrusion. However some "bands" indicate it may be OK some of the time. That indicates intermittent extrusion effects.
Have you calibrated the X/Y/Z axis. Have you calibrated the extruder.
How much does the temperature vary from the target temperature. Is the temperature reading correct - may want to try hotter.
Do you have a cooling fan running? Not normally required with ABS.
Ensure all belts are tight and the hot end cariage is secure.
What layer height are you using and what size nozle.
Direct extuder or bowden ?
What print speeds etc?

You may also want to check filament retraction as it can cause wicking.