Zikr & Dua

Using a Tasbeeh

Q: Is it permissible in Islam to do zikr on a Tasbeeh because some one said that our Holy Prophet (Sallallahu Alayhi Wasallam) never used a Tasbeeh in his life. 

Reciting Durood a Thousand Times

Q:

  1. I came accross a hadith that says one needs to read a specific durood a thousand times and he will not leave this world until he sees his abode in jannah (something to the effect). Is there any hadith that says any durood could be read including the durood "Sallallahu Alayhi Wasallam" and one will get the same benefit? 
  2. I read at least one friday (begining from the thursday night) 1000 times "Sallallahu Alayhi Wasallam". Now am I guranteed jannah because we do not doubt what our prophet Muhammad (Sallallahu Alayhi Wasallam) said?