Correct

仍 vs 仍然 vs 仍旧

/ réng vs réngrán vs réngjiù /
Strokes

Definition

仍, 仍然, and 仍旧 are all Adverbs, and 仍旧 is also an Adjective, which means [still; as before].

Example

仍, 仍然, 仍旧 (Adverbs) all mean "a situation or thing, etc. remaining the same as before".
In the examples the three words are interchangeable, but 仍 is mostly used in literary language, and 仍旧 is more colloquial than 仍然.
1
shí
几十
nián
le
  
,
réng
  
(
réngrán
仍然
  
)
  
(
réngjiù
仍旧
  
)
zhù
zài
yuánlái
原来
de
fāng
地方
  

For decades, he still lives in the same place.

2
Jǐnguǎn
尽管
dào
遇到
hěnduō
很多
cuòzhé
挫折
  
,
réng
  
(
réngrán
仍然
  
)
  
(
réngjiù
仍旧
  
)
hěn
guān
乐观
  
hěn
xìn
自信
  

Though he faced a lot of setbacks, he was still optimistic and self-confident.

3
Lǎo
fángzi
房子
de
jiā
家具
réng
  
(
réngrán
仍然
  
)
  
(
réngjiù
仍旧
  
)
àn
yuányàng
原样
bǎifàng
摆放
zhāo
  

The furniture in the old house is displayed in its original order.

仍, 仍然, 仍旧 (Adverbs) all mean "a situation or thing, etc. being restored to its original state after some alterations".
4
Shǒushù
手术
hòu
  
,
de
bìng
réng
  
(
réngrán
仍然
  
)
  
(
réngjiù
仍旧
  
)
jiàn
不见
hǎo
  

He has shown no sign towards recovery, even after the operation.

5
Zuò
wán
cāo
de
xuésheng
学生
réng
  
(
réngrán
仍然
  
)
  
(
réngjiù
仍旧
  
)
huí
jiàoshì
教室
shàng
上课
  

Those who have finished doing the exercise, please go back and have classes in the classroom.

仍旧 (Adjective) means ”as before (mostly used in books and periodicals) which is a literary expression".
6
Zhè
běn
shū
zàibǎn
再版
shí
  
,
zhǐshì
只是
xiǎobiāo
小标题
lüè
yǒu
gǎidòng
改动
  
,
其他
nèiróng
内容
réngjiù
仍旧
  

The second edition of the book keeps the same except for the changes in its subtitles.

7
Wén
文字
gǎi
le
xià
  
,
chā
插图
réngjiù
仍旧
  

The illustrations kept the same and only the text made a few changes.