Is the new bank entitled to demand the guaranteed amount from the guarantor after the original bank merged with another bank, and is the guarantee affected by a change in the creditor?

If the guarantee is for an interest-based loan from a traditional bank, it is forbidden. The guarantor must repent and withdraw the guarantee if possible, and advise the borrower to rid himself of his forbidden loan. However, if the guarantee is permissible for a transaction that is not forbidden, then it is allowed and entails reward.

The sale or merger of a company transfers its assets and liabilities to the new company. The new bank has the right to demand the guaranteed money. In the case of an interest-based loan, the bank has the right to demand only the principal amount, without the interest, due to the saying of the Prophet, peace and blessings be upon him: "The Riba of the Ignorance period is abolished."