Hii

No it is not possible to change the signature in NEET Application unless and until it is rejected by the authorities and you are asked to change the uploaded signature.
Also one time correction option is available to make required corrections but the option is available for use only once. if you make correction once, you will not be given any more chances.
And also once the time period of correction is over, you wont be allowed to make any more changes in your application.
For more details refer to following link
https://medicine.careers360.com/articles/neet-2019-application-form-correction-guide

Thanks!!