gotta=got to (相当于have to 不得不,必须) ,have got to 必须,不得不.所以也可以写成 have gotta.
There gotta be something wrong = There's got to be something wrong= There's gotta be something wrong.
现在回答你的第一个问题,因为something是单数,所以要用第三人称,所以用 has got to.另外,has 可以缩写,但是缩写了有点不正式,口语常用,书面上不常这么写.
望采纳,祝开心~!