Quastions about Dura-ace 25th group

[Gothard]

I am about to buy a 25th DA groupset for the 20th CSI.
Can the STI Brifters be converted to 10 speed? Not that I am hellbent on it, but I wonder?
Can the rear der cage be swapped for a long cage? (These pesky mountains...)
From what I gather the rear hub being 9sp. will accept a 10cog cassette?

[Steve Hampsten]

Good

No

Don't even think about it

Yes

[Big Dan]

Shimano 8 speed is awesome.......

:)

[Gothard]

LOL!
Thanks!