Particulars for a Spouse that Abandoned Permanent and Long-Term Residency (I-407)

I am a US-citizen, and my spouse received Permanent Residency (Green Card) in late 2007 and also an SSN around that time. We've filed all tax-returns as Married Filing Jointly. She worked only for a couple of years, earning minimum wage. In late 2015, we moved abroad, as per an open-ended reassignment by my employer. Due to uncertainty and potential difficulties in occasionally visiting US, she, in late 2018, via I-407, abandoned her Permanent Residency (from a US-consulate abroad). While married, we've filed every year's tax-return jointly (Married Filing Jointly).

Questions:

 

1. First and foremost, did that abandonment *automatically* invalidate/cancel her SSN? I suspect not (though my search revealed no clear answer). I also hope not, as she's continued to use that SSN in filing our joint tax-returns ever since. Regardless of whether it was cancelled automatically, is it now considered dead, only awaiting a manual, necessary cancellation (by, for instance, calling SSA) by her? If it is cancelled or considered dead, what to do (e.g. apply for ITIN), especially in regard to following questions?

 

2. Must we amend all tax-returns since the abandonment in late 2018 (2018, 2019)? I suspect so, to at least *formally* declare our choice to treat her (a non-resident alien, upon submission of I-407) as a resident. In essence, we had made this choice without making the formal declaration. In other words, we continued filing joint tax-returns using her SSN, without making the actual, explicit declaration in a note attached to the tax-return. If we must amend, can TurboTax Deluxe 2018 and 2019 (desktop-version) handle this?

 

3. Given that, as per my preface, she would be considered a Long-Term Resident, should she have filed, for 2018 (the year of said abandonment), Form 8854 (Initial and Annual Expatriation Statement)? If we are electing to treat her as a resident, then has she, at least in the eyes of IRS, really expatriated??? Neither she nor I are anywhere close to being a Covered Expatriate, but, from my reading, it seems as though she needs to file the form, at least for the initial year, as it seems mandatory upon termination/abandonment of residency. I could not find, in the instructions of this form (8854), any reference to the choice of treating a non-resident alien as a resident. If she must file this form, may it be done through an Amended Tax-Return; and, can TurboTax handle it?

 

4. Are there any other salient points of which I should me made aware? I am looking to minimize tax and frustration. As she hasn't had a salary for multiple years and doesn't expect to have one in the future, treating her as a resident seems only beneficial and tax minimal. Continuing to use TurboTax, and its e-file, from abroad would be least frustrating.

 

Many thanks.