Did we have evidence early on in 2020/21 that the spike protein (COVID virus) & S1 sub-unit protein & we can then extrapolate to the mRNA technology based gene injections, crossed blood-brain barrier?

Yes, in the rodent mice model, we had clear evidence, here is Rhea et al. as an example; intravenously injected radioiodinated S1 (I-S1) spike readily crossed the blood-brain barrier in male mice

SOURCE:

https://pubmed.ncbi.nlm.nih.gov/33328624/

‘show that intravenously injected radioiodinated S1 (I-S1) readily crossed the blood-brain barrier in male mice, was taken up by brain regions and entered the parenchymal brain space. I-S1 was also taken up by the lung, spleen, kidney and liver. Intranasally administered I-S1 also entered the brain, although at levels roughly ten times lower than after intravenous administration…

APOE genotype and sex did not affect whole-brain I-S1 uptake but had variable effects on uptake by the olfactory bulb, liver, spleen and kidney. I-S1 uptake in the hippocampus and olfactory bulb was reduced by lipopolysaccharide-induced inflammation. Mechanistic studies indicated that I-S1 crosses the blood-brain barrier by adsorptive transcytosis and that murine angiotensin-converting enzyme 2 is involved in brain and lung uptake, but not in kidney, liver or spleen uptake.’