Hi Anil,
To clarify your questions:
1- . Can we maintain different Dep Rate in different Ledgers? - Yes possible.
2- Can we have Ledgers based CO Cycles ? - Not possible according to the current SAP Design as its only leading ledger that is connected to Controlling application component. I don't think even in near future, this change is a possibility that SAP will come out of that.
3- What about Sub Ledgers where ledger based posting are not allowed? - I am in agreement with Van.
4- Shall I follow Account Approach or Ledger Approach?? - Using the Account or Ledger approach has their own pros & cons and you have to be aware about that before you make a decision which approach you want to follow.
Thanks & Regards
Subhasish