The first line of the first paragraph: behind is changed to next to not using behind.
the second line of the first paragraph: the correct word is is located, located is the past tense, and the tense is wrong.
but the most commonly used form is: remove the province and directly locate in ...
The first two sentences should be like this: located in the southernmost part of China,
Hainan is the second largest island next to Taiwan in China.
Note: Southern most is authentic, not southest；;
it's not Located in the southest province, which is a mistake.
The first line of the second paragraph: become is an instantaneous verb, but since is a long-term state, and the two do not match.
This sentence should be changed to as a province established in 1988 ...
The second line of the second paragraph: lone error, it is only；; Province and level should be hyphenated: it is the only province-level .....