Depends... if you are contract staff under Maxis HR, you will get most of the benefits as much as what those permanent positions have which including Performance Bonus, Phone Allowances, Medical cover etc., but no contractual bonus for sure.
But if you are offerred contract position which not under Maxis HR, you will not enjoy Maxis employee benefits. Your benefits will very much depends on the 3rd party company you attached to, but i believe you would enjoy a slight lower phone allowance and less attractive medical expenses reimbursement.

Yes... start with contract position, so if you can perform well, they 'might consider' convert you as a permanent staff.
Well... this is the trend of the current market... lots of contract position especially IT industry.