Why can't you attach files when replying to email? Geez!

Tell Apple, this is a user to user forum, no one from Apple is here:

http://www.apple.com/feedback/iphone.html

You can attach a photo or multiple photos to an email after beginning a reply, a forward, and after starting a new email.

Leave the message, go to photos, select the icon at the top right of the photos window, select the photo or photos you want to attach to the message followed by selecting Copy at the bottom right, return to the email, select the body of the email and select Paste to paste the copied photo or photos in the body of the message.

Apps on the iPhone are pretty much sandboxed, with some exceptions. This means that any given app can only see files associated with that app. You cannot share any files between apps.

You can't do this:
1) Download a file from Safari and save it (app number 1)
2) Edit that file (e.g. word processor) (app number 2)
3) Copy that file (e.g. file explorer) (app number 3)
4) Open an email and attach the file to it (app number 4)

etc, etc.

You also can't save files associated with an app, delete that app and reinstall it, and then restore those files. If you could do this, you could do a "restore as a new phone" to fix whatever problems you might be having, but not lose anything in the process.

The iPad can't do this either, which eliminates it as a laptop replacement.