List of iOS devices
iPhone

Model
Announced
Released
Discontinued
Unsupported
Months supported to date
iPhone
January 9, 2007
June 29, 2007; 11 years ago
July 11, 2008; 10 years ago
June 21, 2010; 8 years ago
35 months
iPhone 3G
June 9, 2008
July 11, 2008; 10 years ago
June 7, 2010; 8 years ago
March 9, 2011; 8 years ago
31 months
iPhone 3GS
June 8, 2009
June 19, 2009; 9 years ago
September 12, 2012; 6 years ago
February 21, 2014; 5 years ago
56 months
iPhone 4
June 7, 2010
June 24, 2010; 8 years ago
September 10, 2013; 5 years ago
September 17, 2014; 4 years ago
50 months
iPhone 4S
October 4, 2011
October 14, 2011; 7 years ago
September 9, 2014; 4 years ago
September 13, 2016; 2 years ago
58 months
iPhone 5
September 12, 2012
September 21, 2012; 6 years ago
September 10, 2013; 5 years ago
September 19, 2017; 19 months ago
59 months
iPhone 5C
September 10, 2013
September 20, 2013; 5 years ago
September 9, 2015; 3 years ago
September 19, 2017; 19 months ago
47 months
iPhone 5S
September 10, 2013
September 20, 2013; 5 years ago
March 21, 2016; 3 years ago
Supported
67 months
iPhone 6 / 6 Plus
September 9, 2014
September 19, 2014; 4 years ago
September 7, 2016; 2 years ago
Supported
55 months
iPhone 6S / 6S Plus
September 9, 2015
September 25, 2015; 3 years ago
September 12, 2018; 7 months ago
Supported
43 months
iPhone SE
March 21, 2016
March 31, 2016; 3 years ago
September 12, 2018; 7 months ago
Supported
36 months
iPhone 7 / 7 Plus
September 7, 2016
September 16, 2016; 2 years ago
In production
In production
31 months
iPhone 8 / 8 Plus
September 12, 2017
September 22, 2017; 19 months ago
In production
In production
19 months
iPhone X
September 12, 2017
November 3, 2017; 17 months ago
September 12, 2018; 7 months ago
Supported
17 months
iPhone XS / XS Max
September 12, 2018
September 21, 2018; 7 months ago
In production
In production
7 months
iPhone XR
September 12, 2018
October 26, 2018; 6 months ago
In production
In production
6 months

Question: Wat were the immediate predecessor and successor of the fourth generation iPhone 4?
Answer: IPhone 4 is the fourth generation iPhone, succeeding the 3GS and preceding the 4S.