2. Guess that your mobile hard disk is in NTFS format, and only supports reading but not writing under Mac. You can back up everything in the mobile hard disk, and then convert the format to FAT, so you can read and write under windows and Mac.
3. If you don't understand, just click the email icon to send an email. To send, simply drag the attachment to the email icon.
4. If it is saved in Word Doc format, it can also be opened in Office. But the layout may be different, and Chinese may be garbled.
5.iWork is a general term, including Pages, Keynote and Number, just as Office includes Word, PowerPoint and Excel. Office has a version for Mac. It may not be on the App Store, so it can't be found in the App Store. Not all Mac software is now available in the App Store.