Which statement is incorrect with respect to portability?

1. The estate tax exemption is portable but the decedents remaining GST tax exemption is not.
2. A wife can add her deceased husbands unused exclusion amount to her own basic exclusion amount to reduce her gift or estate taxes.
3. An executor must file IRS Form 706 to take advantage of portability even if the decedents estate is less than $11,580,000 in 2020.
4. Portability limits the amount of exclusion that can be ported to the surviving spouse to $5,000,000.