Hi @Abhishek1602,
First thing, if field is in listview then you can’t set the read_only field.
But your field is not in listview then you can set the field read_only.
Please update the above line.
frm.set_df_property('your_child_table_name', 'read_only', 1, frm.docname, 'hotel_required', child_table.name)
Please set your child table name and other field your according to.
Reference: Please check the whole post.
Thanks!