If I were you, seek a counsel (preferably private lawyer) who will study you contract because if that were the only provisions on your contract, the car, technically belongs to the company and there is no buyer-seller transfer not unless you have fully paid the amount.
1. It depends upon the terms and condition of your contract even if it was only used for work-purposes (It can still be considered a company property unless you have fully-paid it)
2. Yes it is right if you have agreed with it.
What I have encountered with big companies and pharmaceutical companies, their executives/ managers or Sales Representative may purchase his company car same with your company's policy with 60-40 share for 3 years (through salary deduction). But the company may place in the provisions that should the employee resign in less that 3 or 5 years, he must pay the full amount if he wants to get the car or the payments may be forfeited (since the company pays for the maintenance and insurance).
Since it is not stipulated in your contract that you have the freewill to choose the car of your choice, the company can opt to select the car that can be given to you.
Next time, before signing a contract, please have it review/ evaluated first. Contracts are very crucial documents.
Good Luck