Do you like Coldplay's early stuff or more recent?
Definitely Early stuff. Mostly back in the 2000s.
Do you like other alt rock bands?
Yes alt rock is my favorite genre. But most of the bands I like are somewhat old. For example I love Radiohead. How about you?
I'm more of a yacht rock dude like Steely Dan or Rush, what's do you think would be the best Coldplay album to introduce someone to the band?
I would definitely recommend the early 2000s albums. My personal favorite is "A rush of blood to the head" followed by "Parachutes". What's your favorite Steely Dan and Rush album? 
Aja and 2112, some say A Rush of Blood was affected by the contemporaneous 9-11 attacks, do you agree?
I'm not sure if it was exactly correlated with 9/11 but there are many songs that give you the sort of fear or anxious mood. So, maybe.