It didn't take long, did it? :-D Who is FORCING you to do anything? Unlike certain other manufacturers I could mention, Nokia lets you replace almost all of the built-in apps with third party stuff if you want to (heck on Maemo you can replace the whole OS if you want to!). Many of the third party options are even available through the built-in software (for example Share Online lets you upload pictures to Ovi Share or Flickr or Vox). If you don't like Messaging install some other e-mail app. There are plenty of them out there.
Probably because most users wouldn't want to be constantly recharging their phones. Physically bigger screens = less battery life and more expensive hardware
BTW the N900 is higher resolution than the iPhone.
AFAIK no one has confirmed this.