jungmin224 wrote: Also, isn't it possible to back up a Mac to the cloud like backing up an iPhone to iCloud using Time Machine without a separate external device? No, macOS will not back up to iCloud the same way an iPhone will back up. When an iPhone backs up to iCloud, data from your settings to your files will be backed up. You can then choose this cloud backup to restore iPhone to a nearly identical condition as when the most recent backup occurred. More info on iCloud backup for iOS can be seen at How to back up your iPhone or iPad with iCloud - Apple Support macOS will only sync files with iCloud, using iCloud Drive. Typically, this includes anything in your Desktop and Documents folder on your Mac. More information about how iCloud syncing works on macOS can be seen at Set up iCloud features on Mac - Apple Support If you want to do a full system backup on macOS, you'll want to use Time Machine. Time Machine requires either an external drive plugged into the Mac, or some kind of network attached storage. Network attached storage can be a Time Capsule (an Apple AirPort router with internal storage, however these are old now), or a dedicated storage device like a Synology. The easiest way for sure would be to stick with an external drive. More information about how Time Machine works on macOS can be seen at Back up your Mac with Time Machine - Apple Support jungmin224 wrote: And when I read blogs about Recovery and DFU mode while resetting the iPhone, some people say that the difference is quite big, while others say that there is no difference! What I'm curious about as I constantly update my iPhone is that, unlike Recovery mode, DFU mode factory reset destroys all resources! For example, with the iPhone SE, when software 13 was installed at the time of shipment, the current status has been updated to 17. However, if you reset it in DFU mode, it will go back to when it was first released! I wonder if this means that all update history will be saved and the software version will be downgraded to when it was shipped from the factory! Indeed, there is a big difference between the regular restore mode and DFU mode on iOS. DFU mode is intended for use internally at Apple, or at Apple Authorized Service Providers. This mode is used for certain diagnostic and repair reasons. The average person should only need to use the regular restore mode on iPhone. If restore mode, a known good cable, and iTunes or Finder on a Mac can't restore the iPhone, then it may be experiencing other issues. This link from Apple has more information on iPhone restore mode: If you can't update or restore your iPhone or iPod touch - Apple Support jungmin224 wrote: I've been experiencing slowdowns since iOS 16, but after upgrading to iOS 17, I'm even trying to reset it due to battery drain and heat issues. This brings me back to your initial statement. It's possible that your iPhone could need service, or is being affected by other environmental factors. It's normal for iPhone to generate heat as it performs foreground and background tasks, fortunately Apple has taken heat in their devices into delicate and serious consideration when designing their product. This link has some more information about the different heating behaviors of iPhone: If your iPhone or iPad gets too hot or too cold - Apple Support Additionally, you are more likely to notice worse battery life when iPhone is hot. iPhone can also get warm from being in contact with sunlight, even if it's in an air conditioned room. However, it may still be a good idea to bring your iPhone to an Apple Store or Apple Authorized Service Provider. There, a technician can run a diagnose to determine if the hardware of your iPhone is in good condition, and can help you navigate the issues you're experiencing. Apple can be reached at 1 (800)APL-CARE (1-800-275-2273), or on the web at https://getsupport.apple.com I hope this helped!