Future

problems with future

The text is already completed with the answers from the KEY. Please help me interpret them and understand it

Technology has made such dramatic advances in the past decade that by the year 2100 who knows what changes 1.will have taken place? It is quite likely that by 2050 we 2. will have used up most of the earth's natural resources and so we 3. will rely/ will be relying on wind power and hydropower for energy needs. As a result of this shortage of energy, it is quite probable that scientists 4. will have found a way for us to live outside the earth. By the next century it's possible that people 5. will live/will be living in cities on the Moon or perhaps in cities on the seabed. It is to be hoped that scientists 6. will have discovered cures for fatal diseases such as Aids and, due to the advancement of genetic engineering, hereditary diseases passed down from generation to generation 7. will exist no longer. It is quite possible that by 2100 life expectancy 8. will have increased to 100 and that we 9. will be able to enjoy a healthier existence than is now possible. Another area likely to have been further affected by technology in the next years is education. In schools, computers 10. will have repalced teachers and many students 11. will stay/will be staying at home to complete their education. We 12. will see changes in the work-place too. The two main areas of employment 13. will be the so-called creative and caring professions, and the disappearance of jobs in manufacturing 14. will result in massive unemplyment.

I am trying to interpret the answers proposed by KEY:

1. future perfect because of "by the year 2100"
2. future perfect because we have "by 2050"
3. will rely/ will be relying - natural consequence ? something we can't control?
4. i don't understand again . why future perfect ? because of the reference to "BY THE YEAR 2100"? why can't we just say "will find" if we have "quite probable" earlier in the sentence ?
5.we have by-phrase and yet there is no FUTURE PERFECT but future simple/cont ? is it because we express "action in progress at a stated time in future?
6.why future perfect ? do i have to refer again to "by the year 2100" ? namely it will be another thing that scientists will have dicovered?
7. future simple - just prediction about future ?
8. future perfect because of "by 2100"
9. we will be able to - this is speaker's opinion - what he/she thinks or believes ?
10.i don't get it . why future perfect ?maybe because we refer to "by 2100" again ?
11. soemthing that will just happen as a natural consequence ?
12. prediction
13. prediction
14. prediction