The CBB

قرينة qarīna "wife"
carina "pretty"

أستاذ ʾustāḏ "professor, teacher, title of courtesy for an individual of higher education or learning"
usted "you (respectful)"

Maybe a bit of a stretch, but it stood out to me.

1) are there any native non-compound words that are four syllables or longer? ホトトギス hototógisu "lesser cuckoo" is one. I have found some minimal pairs or near minimal pairs for some vowel sequences. I should probably go through my resources though and see what patterns there are and what limitation...

:es-pv: Basque Ziur nago hil zuela. /s̻i.ur nago il s̻u.ela/ [s̻i.ur naɣo il t͡s̻u.ela] ziur n-a-go hil-∅ z-∅-u-∅-en-la sure 1SG-PRES-be kill-PP 3.ERG.3.ABS.PST-SG.ABS-AUX-SG.ERG-PST-COMP I'm sure he killed him. (Hark hura) hiltzen ikusi nuen. /(ark uɾa) ilt͡s̻en ikus̺i nu.en/ [(ark uɾa) ilt͡s̻en ik...

:es-pv: Basque Bi hankaz dabilena etsaia da. /bi ankas̻ dabiʎena et͡s̺ai.a da/ [bi ankas̻ taβiʎena et͡s̺ai.a ða] bi hanka=z d-a-bil-∅-en=a etsai=a da two leg=INSTR.INDEF 3.PRS-PRS-walk-SG-REL=ABS.SG enemy=ABS.SG COP.PRS.3SG Whatever goes upon two legs is an enemy. Lau hankaz dabilena, edo hegoak dau...

:es-pv: Basque Salduko genuen janaria ez daiteke sal, gure sukaldaria ez baitago. /s̺alduko genu.en janaɾi.a es̻ daiteke s̺al | guɾe s̺ukaldaɾi.a es̻ baitago/ [s̺alduko ɣenu.en janaɾi.a es̻ taiteke s̺al | guɾe s̺ukaldaɾi.a es̻ paitaɣo] sal-duko gen-∅-u-en-n janari=a ez d-a-di-∅-te-ke sal | gu-re suk...

:es-pv: Basque Basque forms these types of indefinite pronouns by adding -bait to the corresponding question word. (In some of these cases, the translation depends on which part of the sentence is the focus; I'm assuming that the second sentence in each pair is meant to be an answer to the first.) (...

Basque

Nahi nuelako egin nuen.
/nai nu.elako egin nu.en/
nahi-∅ n-∅-u-en-lako egi-n n-∅-u-en
desire-ABS.INDF 1SG.ERG.3.ABS-SG.ABS-have-PST-because do-PP 1SG.ERG.3.ABS-SG.ABS-AUX-PST
I did it because I wanted to.

:es-pv: Basque Nork egiten du nik baino azkar korrika? /nork egiten du nik baɲo as̻kar korika/ [nork eɣiten du ni paɲo as̻kar korika] nor-k egi-ten d-∅-u-∅ ni-k baino azkar korrika=∅ who-ERG do-PRESP 3.ABS.PRS-SG.ABS-AUX-3SG.ERG 1SG-ERG than fast running=ABS.INDF Who runs faster than me? Inork ez du...

:es-pv: Basque Hilzorian dagoen zuhaitzeko azken hosto bizidunak gara. /ils̻oɾi.an dago.en s̻u.ait͡s̻eko as̻ken os̺to bis̻idunak gara/ [ilt͡s̻oɾi.an daɣo.en t͡s̻u.ait͡s̻eko as̻ken os̺to βis̻iðuna kara] hilzori=an d-a-go-en zuhaitz=eko azken hosto bizidun=ak g-a-ra death.throes=INESS.SG 3.PRS-PRS-be....

:es-pv: Basque Elurra iparraldean egiten du bakarrik, baina euria alde guztietan egiten du. /elura iparalde.an egiten du bakarik | baɲa euɾi.a alde gus̻ti.etan egiten du/ elurr=a iparralde=an egi-ten d-∅-u-∅ bakarrik | baina euri=a alde guzti=etan egi-ten d-∅-u-∅ snow=ABS.SG north=INESS.SG do-PRESP ...

:es-pv: Basque Nola hil nintzen galdetzen dutenean, esaiezu: artean haserre. /nola il nint͡s̻en galdet͡s̻en dutene.an | es̺ai.es̻u ‖ arte.an as̺ere/ nola hil-∅ n-i-n-za-en-n galde-tzen d-∅-u-te-n=ean | e-sa-∅-i-e-zu ‖ artean haserre how die-PP 1SG.ABS-PST-PST-AUX-PST-COMP.Q ask-PRESP 3.ABS-SG.ABS-AU...

:es-pv: Basque Galdetu nuen: «Zergatik ari zara zure emaztea jotzen?» /galdetu nu.en ‖ s̻ergatik aɾi s̻aɾa s̻uɾe emas̻te.a jot͡s̻en/ galde-tu n-∅-u-en ‖ zer-gatik ari z-a-ra-∅ zu-re emazte=a jo-tzen ask-PP 1SG.ERG.3.ABS-SG.ABS-AUX-PST ‖ what-MOTIV PROG 2SG.ABS-PRS-AUX.PL.ABS-PRS 2SG-GEN wife=ABS.SG ...

Not sure if this has been posted here before, but:

si "if"
se (third-person reflexive pronoun)

se "if"
si (third-person reflexive pronoun)

...can you really rule out cases of similarity only due to later sound changes, when those soundchanges are themselves common, or areally common? Okay, that's also a good point, but it just occurred to me that there's another argument against a connection between aurum and urre via a non-Italic IE ...

Basque

Erregeen erregea naiz.
/erege.en erege.a nais̻/
errege=en errege=a n-a-iz
king=GEN.PL king=ABS.SG 1SG.ABS-PRS-COP
I am king of kings.

:es-pv: Basque Hil (al) zenuen? /il (al) s̻enu.en/ hil-∅ (al) zen-∅-u-∅-en kill-PP (Q) 2.ERG.3.ABS-SG.ABS-AUX.TR-SG.ERG-PST Did you kill him? Ez (al) zenuen hil? /es̻ (al) s̻enu.en il/ ez (al) zen-∅-u-∅-en hil-∅ NEG (Q) 2.ERG.3.ABS-SG.ABS-AUX.TR-SG.ERG-PST kill-PP Didn't you kill him? Bai. / Ez. /ba...

However, we also have to bear in mind that Vasconic had been living alongside Indo-European languages, including undescribed Indo-European languages that may well have been closely related to Italo-Celtic, for hundreds if not thousands of years before the era of Latin-to-Proto-Basque borrowings - a...

:es-pv: bi "two" :eng: bi- , :lat: bis "twice" :es-pv: sei "six" :ita: sei "six", :esp: :por: seis "six" :es-pv: urre "gold" :lat: aurum "gold" I'm not sure, given how little we know of proto-Vasconic, if we could make the argument that these are truly not cognates. Apparently bi was originally big...

da "is"
だ da "is, are, am"

haize "wind"
風 kaze "wind"

bi "two"
bi-, bis "twice"

sei "six"
sei "six", seis "six"

urre "gold"
aurum "gold"