RS-TE apartment illegally deregulated?

[TC2024]

First off, thank you for running this forum...it is really an incredible source of information!
Now, here is my predicament:

I moved into my current apartment located on a very desirable street in the UES in June/2020, taking over a lease of the previous tenant (thanks to COVID). Several months ago, my building was sold to a developer (it was previously owned by someone who lived in building and had recently passed away) and they are not renewing any leases citing major renovations. Knowing that there are rent stabilized units in my building, and suspicious that my apartment may be RS as it is by far the most modest, I requested a rent history from the DHCR, which reads:

1984: RS; Amt Miss
Tenant: XX XXX ; Reasons differ./change: IMPRVMNT
1985-1989: "Reg not found for subject premises"
1990-1999: RS-TE; Owner occupied/employee; Exempt
2000-now: "Reg not found for subject premises"

From that information, I surmise that the unit was previously occupied by the superintendent until 1999, then deregulated right after. From my understanding, the apartment can be lawfully deregulated if it met certain vacancy and IAI requirements that causes the rent to rise above a certain threshold; however, from what I glean from another post, http://tenant.net/phpBB3/viewtopic.php?f=3&t=13978&p=58858#p58857, there is some debate whether rent stabilization status would have to be re-institute prior to deregulation. I also tried to look for J-51 and 421a tax abatement for my building to no avail.

So, this poses several questions for me:
1) Even if my apartment was illegally deregulated in 2000, is there anything I can do about it now, 24 years later, given the "four year look back" rule? Does the rule imply that if the landlord can get away with illegally deregulating an apartment for at least 4 years, then they get off scot-free? I care less about recouping overcharges, but moreso maintaining my statutory right to renew my lease.
2) If it was illegally de-regulated, is it possible to reinstate RS status?
3) How can I prove that it was legally or illegally deregulated?
4) Do I have leg to stand on in this situation and should I seek legal counsel? My lease is up in August, and since they are not renewing my lease anyway, I only stand to gain from this.

Some additional information that may/may not matter:
I paid $2,600/mo when I first moved in in June/2020 and it has increased to $2,900 over the past few years. The previous tenant paid ~$2500 when she first moved in Sept/2013, the rent only marginally increased because she had put some of her own money into updating it. I plan to ask my superintendent if he has any information regarding improvements that were made in 2000. The bathroom appears original, and the kitchen appliances may be from the early 2000's.

[jpm1992]

Commenting to follow - I just made a post about a very similar situation. Will follow-up here if I learn anything!

[TenantNet]

We locked the other message pending clarification. Are jpm1992 and TC2024 the same user? If so, we don't permit users to have multiple accounts and the same issue from the same person should not be posted more than once. See the forum rules.

Or did you just point to your message here? Please clarify.

As for the posts, we're behind in answering these kinds of messages. The problem is there are very little ways for tenants to challenge illegal destabilizations, and we end up just repeating ourselves.

[jpm1992]

We're not the same person! I just commented here because it is a very similar situation to my own...RS-TE; Owner occupied/employee; Exempt followed by "Reg not found for subject premises"

[TenantNet]

OK, we unlocked the other post. But as said, we get behind on these more complex questions.

[TC2024]

Thank you!