If Jesus is God, how is he called God's only begotten son?
Because Jesus was God's Only One who became flesh as man and as all other 'sons of men'. God's Only Begotten Son because Jesus took on flesh from a 'fleshless' state..
Flesh? A derogatory term usually for Christians to keep reiterating the idea that this life is garbage and you should instead favor an idea that you can't possibly know is real instead.
A perfect god needs to come up with a plan to set right the ways of man because he didn't foresee this whole mess happening before it happened or else could have gone about it differently?
All knowing yet doesn't know events are going to turn out unfavorable to him so he reacts like a brat child. "I don't like these humans so I'm going to drown everything." Then realized after this plan that he messed up and needs to promise never to drown humans again?
It's all made up human garbage meant for one purpose to keep the dumb in line from becoming assholes.