Ok, so we know that there is an 8 chevron address to get from the Milky Way to Atlantis, and there is a 9 chevron address to get from the Milky Way to the Destiny.
So:
1. If Destiny is millions of years older than Atlantis, why is that a 9 chevron address and not 8 chevrons?
2. Was something previously an 8 chevron address that was later replaced by Atlantis?
3. Could Destiny dial 8 chevrons and get to Atlantis if the power was available?
So:
1. If Destiny is millions of years older than Atlantis, why is that a 9 chevron address and not 8 chevrons?
2. Was something previously an 8 chevron address that was later replaced by Atlantis?
3. Could Destiny dial 8 chevrons and get to Atlantis if the power was available?