I finally moved (about 2 years after starting my immigration process - but with a deliberate 18 month delay due to a change in family circumstances) last week. So I thought I'd share my POE experience. I flew BA and the plane was mostly full of tourists, which meant the immigration line was huge for visitors and super short for US citizens. i was about to join the lengthy non-US citizen line when an official noted my children's US passports and told us to join the US Citizen line. Instead of having 200 people in front of me, I now had two. The immigration officer was super friendly (that's a first for me!), stamped my passport, took my fingerprints and photo, gave me some advice on getting a social security number and wished me well. No secondary. All in all, took about 2 minutes.

If you were previously an LPR, as per your .sig, then you already have a Social Security Number. No need for a new one.

I know. But thanks for mentioning it.

It might be a good idea to see that your most recent admission was under the same A-number you had previously. If not, this might cause delay in future naturalization.

I have no idea if there is a procedure to combine files in advance of subsequent application.