Christine 15As

A1. It is called 'individuation' or 'identity formation' in psychological terms. 

http://www.psychology24.org/psychological-reasons-that-teenagers-get-tattoos/amp/

A2. True but there're more reasons that people get body modifications like: to express individuality, to enhance attractiveness and sexuality, for love of the art, to create a personal narrative, to develop physical endurance, to show an affiliation or commitment,  in search of spiritual enlightenment, as sign of resistance, impulse or due to addiction. 

http://info.painfulpleasures.com/blogs/psychology-body-modification

A3. Look good, feel good. Body modification will boost self esteem. 

https://yogapanther.wordpress.com/2012/06/18/does-body-modification-really-boost-self-esteem/amp/

A4. You can hide scars with tattoos. 

https://www.pinterest.com/explore/scar-cover-tattoo/

A5. Tattooing is now pop culture. 

http://m.huffpost.com/us/entry/6053588

A6. Ear piercings are the most popular followed by nose piercings and belly button piercings. 

https://www.google.co.jp/amp/s/m.mic.com/articles/amp/127375/facial-and-body-piercings-yeah-theyre-all-back

A7. In terms of cosmetic surgery, yes. 

https://www.plasticsurgery.org/cosmetic-procedures/facial-implants

A8. 2% of the population have tattoos. 

http://biz-journal.jp/i/2017/03/post_18410_entry.html

A9. 3 billion, five hundred seventy-five million, four hundred eighty six thousand, nine hundred and sixty two people in the world have tattoos. 

https://www.quora.com/How-many-people-in-the-world-have-tattoos

A10. 17% regret getting tattoo. 

http://www.statisticbrain.com/tattoo-statistics/

A11. $45 for a small tattoo and $150 for a large one. 

http://www.statisticbrain.com/tattoo-statistics/

A12. Depends on the surgeon but tattoo removal cost ¥2200 per square inch in Japan. 

http://www.s-b-c.net/charge_list/tattoo.html

A13. Some facial implants are made from silicone. Concerns have been raised about the safety of silicone implants. Currently, there is no clear scientific evidence that silicone is a harmful substance.

https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/facial-implants

A14. You can get serious infections from unhygienic practices or from equipment that isn't sterile,  infections can also result from ink that was contaminated with bacteria or mold. 

https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm048919.htm

A15. Sometimes bad infections, such as human immunodeficiency virus (HIV) and hepatitis, can be spread by body piercing. Other problems may include bleeding, swelling, scarring, and reactions to the jewelry

http://www.aafp.org/afp/2005/1115/p2035.html