iPhone 7 Plus gets hot

Your device might get warm

When you use the device or charge the battery, the device might get warm. You might notice that your device feels warmer in these situations:

• When you set up your device the first time
• When you restore from a backup
• When apps reindex or reanalyze data, like Photos tagging for faces, places, or keywords after a software update

These conditions are normal, and your device will return to a regular temperature when complete.

Here are some of the higher ambient-temperature conditions and activities that might cause the device to change performance and behavior:

• Leaving the device in a car on a hot day.
• Leaving the device in direct sunlight for an extended period of time.
• Using certain features in hot conditions or direct sunlight for an extended period of time, such as GPS tracking or navigation in a car, or playing a graphics-intensive game.

Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures - Apple Support
To answer your second question about closing recently used apps, this won't be necessary unless one of your apps becomes unresponsive. Take a look at this information:

Force close an app

When you double-click the Home button, your recently used apps appear. The apps aren’t open, but they're in standby mode to help you navigate and multitask. You should force an app to close only when it’s unresponsive.

Force an app to close on your iPhone, iPad, or iPod touch - Apple Support

I Collected my new iPhone 7 plus rose gold on 25/09. Only few days , and I also feel the phone very hot. it seem like abnormal .. any solution?

None of the Above . i am just normal usa in office .

I just purchased 4 new iPhone 7's - every single one of them gets Extremely hot when on a charger and the battery life is AWFUL 😟 NOT COOL APPLE

I had to take mine to Apple store due to it being hot while using the phone. The technician resat my software as he could not find the possible cause if it, and the high temperature was not registering. That said, I was on the phone last night and was on speaker and my phone started to get quite hot again. Also, been noticing cell signal loss frequently. Needless to say, I will be calling Apple Care today. Iphone 7 seemed to be problematic - I have using iphone for 4, 5 and 6 plus and never had issues.