Is it possible That The process that had occurred with the flood have actually petrified ginormous tree stumps during the flood??
...the process that had occurred with the flood...
I'm assuming that you are talking about the biblical flood. There is no evidence that the flood had ever occurred.
Can...mountains actually be Giant petrified Tree Stumps?
No. Petrified trees are made of silica with a very distinct texture as observed in the microscope. All mountains are made of other things. For example, granite, limestone, basalt, and various types of rock. Some mountains are made of sandstone quartzite, which are compositionally similar to what petrified wood is made off. However, sandstone is just hardened sand, and quartzite is sandstone that has become even more hardened due to the high temperatures and pressures deep in the Earth. They looking nothing like petrified wood.
I think I know what you are talking about. There are geological formations called volcanic plugs, which bear a strong resemblance to gigantic tree stumps and might easily fool people who knew nothing about geology into thinking that's what they were. Many millions of years ago the magma inside a volcanic cone cooled and solidified, and the volcano became extinct. During the course of millions of years of weathering, the softer, outer parts of the volcano were eroded away, leaving just the harder core still standing. Edinburgh Castle is sited on top of one of these volcanic plugs, but the presence of the castle disguises its tree-stump-like appearance. This particular volcanic plug is about 350 million years old. I don't think there are any which are three kilometres high, this one certainly isn't. Devil's Tower in Wyoming USA is a good example of the kind of plug I mean, but I have seen better ones (see Wickepedia). Anyone with a knowledge of botany would know that a tree of such dimensions would be a physical impossibility.