What will be the treatment of expenses like car rent, office rent etc before company registration?

Pre opertating Expense and shuld be write off accordingly..

these are considered as preliminary expenses and written off every year according to the company's policy.

Should be accounted as an Pre Operating Expenses in a profit & Loss account..

Expences incurred before commencement of Business.  Allowable business expences are expences that you can claim as dedeuction.

Preoperating expenses are expensed

These are pre-operative expenses and has to be capitalized and write off accordingly

Here one thing need to be clarify that what is pre-operative and preliminary expenses 

Pre-operative==expenses before operation /establishment start preliminary==introductory, preparatory expenses after establishment.