From the statements made by you, it is difficult to give an opinion on the workings of your CA. The following general principles may, however, give you an understanding of the situation broadly described by you.
1) The employer's contribution to PF is not taxable, provided it is within the limits specified under the Income Tax Act. In your case, the employer's contribution can be assumed to be within the limits and hence not taxable in your hands.
2) You might have claimed deduction u/s 80C in respect of your contribution, as mentioned by you.
3) The interest on PF is not taxable.
4) The PF received by you during FY 2015-16 is not taxable.
5) The rebate u/s 89(1) applies when you receive arrears of salary. This is basically to even out the additional tax that may arise due to the change in the slabs because of lump sum receipt. In your case, there appears to be no need for relief u/s 89(1).