yes, the mental process w/ environmental conditions direct the composition of future offspring's.
No. DNA directs composition of future offspring. You've been watching too many action cartoons. Our minds and environment cannot change our molecular structure.
I do not understand why you are stuck on this idea that the individual's "mind" is the key to the possibility or lack there of in the theory of evolution. We do not know exactly why the giraffe developed a long neck and legs. It seems to me that "thinking" it needs to be taller would be one of the least likely reasons.
Males and females do make choices in breeding. Sometimes there is cross breeding. There are plenty of ex amples of freaks of nature. It is possible that short neck giraffes were considered "runts" and less desirable mating selections. In THAT sense the individuals "minds" would come into play as a determining factor.
Physical traits not common to all members of a group can and are multiplied by selection of the individuals in breeding. Availability or lack there of in breeding choices probably play into the rise of abnormal physical traits also.
It is possible that the giraffe had a specific diet and was confined to a specific area and short giraffes starved.
My point is that there are many possible reasons how and why physical changes occurred.
"God" designing the modern giraffe and plopping it down on the modern African Savannah is a silly possibility. At some point we should reject some theories because they are less science and more catering to the wishes and fantasies of some confused people.