Is a marriage contracted without a guardian (wali), but in the presence of the mosque's imam and witnesses, yet without a documented marriage contract, considered Islamically valid? If not, what are the necessary steps to rectify it, and is it obligatory to renew the contract with the possibility of adding new conditions?

For a marriage to be valid, it must be contracted by the woman's guardian (wali). If the closest guardian refuses to marry her to a suitable man, the guardianship transfers to the next in line. If all of them refuse, then the Shariah judge, or whoever acts in his stead, shall marry her. If the offer and acceptance are made in the presence of two witnesses, the marriage is valid, even if it is not written in an official contract.