Your spelling sux!
I would not recommend MDF as a kitchen countertop unless you are intending to use it as a foundation for some type of cement board upon which you are attaching tile. If that IS the case I would recommend 3/4 " thickness.
Medium Density Fiberboard. Wood fibers mixed with resin and pressed into sheets. Much better than particleboard.
As an underlayment for flooring MDF will work. Personally I find that regular plywood is more cost effective for that purpose.
Yes, you can paint it like any other panel. I recommend a primer first or you can use a light first coat of your paint.
It is extremely heavy compared to plywood. Unlike dimensional lumber, the 3/4" thickness is actual, not nominal. It weighs around 95lbs. So I was able to move whole sheets by myself by wrapping a ratchet strap about 1/3 from each end, to make it easier to lift it and manuever it to my cutting area. OTherwise, two people would be highly recommended for handlling full sheets.
2 cuts are free. Need more. Buy a skil saw. Trust me.