Your first four questions are related to the careers in both the fields, for detailed introduction of both of these fields, You must visit the career introduction section available at eduvision website. Or you may also go directly to this link http://www.eduvision.edu.pk/careers/index.php?id=52
for detailed introduction of career in Biotechnology. Similarly detail introduction with job opportunities of Biochemistry may be found here http://www.eduvision.edu.pk/careers/index.php?id=44
Both are very good fields. Biotechnology, is an emerging sciencces, and has good scope all over the world which is increasing day by day. Its applications are being used in numerous field. It is estimated that only in the field of medicine, by 2020 more than 50% of the medicine will be prepared with the help of biotechnology.
Regarding the status of University of Lahore, it is a recognized and well reputed university. But if you can also apply to University of the Punjab and Government College University Lahore, that will be better. I am not saying that you should not apply in University of Lahore, but if you get admission in PU or in GCU then you should prefer these two over University of Lahore. After these two, university of Lahore is good option.
Sohaib Ahmad Khan