Recently, Apple has admittedly been slowing down the performance of older versions of IPhones to prevent malfunctions. However, it is easy to see if your phone is being 'slowed down' by Apple. According to a Business Insider article, IPhone users must first download an app that tells you the speed of your IPhone's main chip.
No need to check as soon as they came with 10 my 7 start acting up. Another weird thing a friend told me he found a hack and made his phone from 16g to 120g without installing any hardware
Seriously? Do you know how he did that? Also, I believe Apple was doing this to increase their sales of IPhone X's. However, it has not worked because of the recent news of them not meeting their projected sales.