How can i use multiple requests and pass items in between them in scrapy python

No problem. Following is correct version of your code:

def page_parser(self, response):
      sites = hxs.select('//div[@class="row"]')
      items = []

      request = Request("http://www.example.com/lin1.cpp", callback=self.parseDescription1)
      request.meta['item'] = item
      yield request

      request = Request("http://www.example.com/lin1.cpp", callback=self.parseDescription2, meta={'item': item})
      yield request

      yield Request("http://www.example.com/lin1.cpp", callback=self.parseDescription3, meta={'item': item})

def parseDescription1(self,response):
            item = response.meta['item']
            item['desc1'] = "test"
            return item

def parseDescription2(self,response):
            item = response.meta['item']
            item['desc2'] = "test2"
            return item

def parseDescription3(self,response):
            item = response.meta['item']
            item['desc3'] = "test3"
            return item