Is the sale considered valid if a man bought land in installments from a company, paid an advance, then paid the installments annually with an agreed-upon increase in case of delay, then the original seller transferred ownership to a third party for a sum of money, and the third party completed paying the installments under the same system, then paid the remaining amount in a single lump sum?

Installment sales are permissible, but the transaction included a corrupt condition, namely the application of interest on overdue amounts, which is forbidden usury (riba). Nevertheless, the contract is valid, and the condition is void. Therefore, your purchase and sale of the land is valid, and you must repent to Allah for entering into a contract that included a usurious condition, because Allah has forbidden usury and threatened those who engage in it with war.