If it’s common area Parking and not a sold parking under rera then it can’t be permanently allotted 

1. All 20 stilt parking spaces shall be integral part of the flat and shall always remain with the occupant or owner of the particular flat. Such parking shall never be open for any further allotment.

2. Open space cannot be covered by PVC sheet etc. You can plant some tree or can use car cover in alternate.

You would have not been sold parking slot but only allotted 

you cannot sell stilt car parking slot 

3) you need muncipal corporation and bmc permission for covering of parking slot 

Allotment and transfer of parking slots: The rules for the allotment and transfer of parking slots can be determined by the cooperative society's bylaws or any specific regulations applicable in your jurisdiction. In some cases, parking slots may be allotted to specific units or owners and can be transferred or sold along with the unit. However, this can vary, and it's important to review the society's bylaws or consult with a local attorney to understand the specific rules governing parking allotment and transfers in your society.

Covering open parking slot: Whether you have the right to cover your open parking slot with a PVC sheet supported by rods would depend on the specific rules and regulations of your cooperative society. Some societies may have restrictions on modifications or changes to common areas, including parking spaces. It's advisable to review the society's bylaws or consult with the society's management committee or a local attorney to understand the rules and regulations regarding modifications to parking spaces.

In any case, it's recommended to communicate with the society's management committee or the designated authority to seek clarification on these matters. They can provide you with information on the specific rules and regulations applicable in your society and guide you on the process for obtaining any necessary approvals or permissions.

If the builder has given an allotment letter in favor of the owners allotted with the stilt parking space, then society cannot take away the  rights if the member already paid the charges for the said parking and an allotment letter has been issued in his favor.

However the stilt parking cannot be sold as independent unit.  It is the aprt of the flat hence it will be the part of sale deed.

2.  For constructing even a shade over the open parking space, the society's permission need to be obtained.

1. If the seller was having facility of slit parking , then with the transfer of the flat , the said  parking will also transferred , and he having no authority to sell the said parking 

- Hence, you can approach the management of the society to allot the said slit parking. 

2. Without the approval of the society , you cannot cover the open parking , as it come under the common area of the society. 

Parking will sell to next buyer.

parking slot with a PVC sheet supported by two rods ? - You has purchased the flat knowing all situation in advance. so cannot claim any relief as matter of right but with the consent of the CO society. 

1. Car parking slots cannot be sold. An open car parking in a stilt floor comes under 'common areas' meant for the use and enjoyment of all residents, and no one can claim any exclusive slot legally.

2. If your society has no objection, you may do so.