how to replace certain pages with one page at the same time ?

First get the path to the document you are using for a replacement by opening it and running the following script in the console:

this.path;

Next, open the document for which the pages will be replaced.  Run the following script in the console, adding the path from the previous step betweent the quotes:

var pth="";

Run the following lines of code in the console:

this.deletePages(3); this.insertPages(2, pth, 0,0);
this.deletePages(15); this.insertPages(14, pth, 0,0);
this.deletePages(49); this.insertPages(48, pth, 0,0);
this.deletePages(59); this.insertPages(58, pth, 0,0);

The 0,0 is the page range of the document to insert (that is, page 1).  If it is another page, change these using the zero-based index of the page.

Or you can use this:

this.replacePages(3, pth, 0,0);
this.replacePages(15, pth, 0,0);
this.replacePages(49, pth, 0,0);
this.replacePages(59, pth, 0,0);​

This also assumes page 1 of the source document is used.