BTW just to follow up
” And lastly and mainly, does Secession = treason or altogether legal”
Dont forget Salmon chase said it was nOT legal (you implied th oppoiste, just want to make sure youre clear on that)
Also I looked up your hint : US Public Law 85-425 sec 410, and Im not sure why I had 1930’s in my head but it wasnt until 1957 (!!! almost a century after the war) when the were granted pensions and the last confederate vet died in 1959 so the answer to your question “did Confederate soldiers receive any USA pensions, as all soldiers receive?” is no. Though a few did.