Is the contract permissible in Islamic law given the existence of a condition that was not disclosed before entering into the project, and is it permissible for the participant to request the return of the capital and the profits received?

The contract of ijarah (lease/hire) is a binding contract, and it may not be revoked except by mutual consent, unless the two parties agreed upon the right of revocation at the time of contracting. As for the contract of partnership (sharikah), it is a non-binding contract, which may be revoked at any time, so long as it does not cause harm to others. Upon dissolution of the partnership, the partner is entitled to his capital and his share of the profits, and he does not bear the loss of capital. If deception or fraud is proven in the partnership, then it is considered void, and each partner is entitled to his capital and profit, and he owes remuneration for his work if he had worked.