Is it compatible with the iphone?

This earbuds fit with any device with 3.5mm jack, devices without a 3.5mm jack, like the iPhone 7, 8, X, require an adapter.

Do these work for small ears?

Yes, these earbuds would work for small ears, they come with 3 different size replacement attachments.

Will these fit a Samsung tablet?

As long as it has a 3.5MM jack. The plug is a universal size. They fit with phones, MP3 players, tablets, etc.

Is the jack straight or bended?

The jack is straight.

Do they have volume control?

There is no physical volume control on these headphones, but have a call button with microphone for answer/reject calls, next song, previous song.

Do they reduce outside noise?

Yes, nice soft silicone eartips will will form a seal around your ear and you will be able to isolate and block some external noise better.