Objective -c POST request not working - ios

Question

i develop program which searches for similar images(Reverse image search)
My Code:
Y_request = [[NSMutableURLRequest alloc]init];
[Y_request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
[Y_request setHTTPShouldHandleCookies:NO];
[Y_request setTimeoutInterval:30];
[Y_request setHTTPMethod:#"POST"];
NSString *Y_boundary=#"myBoucndary";
NSString *Y_FileParamConstant=#"upfile";
Y_requestURL = [[NSURL alloc]initWithString:#"https://www.yandex.com/images/search"];
NSString *Y_contentType = [NSString stringWithFormat:#"multipart/form-data; boundary=%#",Y_boundary];
[Y_request setValue:Y_contentType forHTTPHeaderField:#"Content-Type"];
Y_body = [NSMutableData data];
NSDictionary *Y_params=#{
#"format":#"",
#"request":#"[{\"block\":\"b-page_type_search-by-image__link\"}]",
#"rpt":#"imageview"
};
for (NSString *Y_param in Y_params) {
[Y_body appendData:[[NSString stringWithFormat:#"--%#\r\n",Y_boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[Y_body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"%#\"\r\n\r\n", Y_param] dataUsingEncoding:NSUTF8StringEncoding]];
[Y_body appendData:[[NSString stringWithFormat:#"%#\r\n", [Y_params objectForKey:Y_param]] dataUsingEncoding:NSUTF8StringEncoding]];
}
// add image data
NSData *Y_imageData = UIImageJPEGRepresentation(imageSearch, 0.1);
if (Y_imageData) {
[Y_body appendData:[[NSString stringWithFormat:#"--%#\r\n", Y_boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[Y_body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"image\"; filename=\"image.jpeg\"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[Y_body appendData:[#"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[Y_body appendData: Y_imageData];
[Y_body appendData:[[NSString stringWithFormat:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}
[Y_body appendData:[[NSString stringWithFormat:#"--%#--\r\n", Y_boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[Y_request setHTTPBody:Y_body];
[Y_request setURL:Y_requestURL];
[_myWebView loadRequest:Y_request];
This Yandex Search query. This query works only on the iPhone but does not work for Ipad,Why?.
Thanks for the answer.