Hello,
1) If the agreement says that Podium/stilt parking space 161 is allotted to you you it is your right to get the same.
2) If he is providing you covered parking and if that is not acceptable to you as an alternate parking solution, you need to take legal steps against the builder/promoter.
3) As you mentioned it is possible that the builder is double dealing and selling the stilt parking to someone else at a higher rate.
4) You need to send a legal notice to the builder demanding the allotted/purchased stilt parking to be made available to you.
5) If the builder does not comply you can approach the District Consumer Forum for deficiency of service as the builder is a service provider.