Mojang (Classic)-Cape

You had to work at Mojang. The cape was an employee perk, and minecraft.wiki lists it as going to anyone on staff between December 20, 2010 and October 7, 2015. It was never sold, never given as a code and never tied to an event, so players outside the company had no way to earn it.

No. Mojang stopped issuing it in October 2015, when a redesigned Mojang cape replaced it as the staff cape. That cape was later replaced too, by the Mojang Studios cape in July 2021. Accounts that already had the classic version still show it, but nobody receives it today.

They are two generations of the same staff cape. The classic one was handed to Mojang employees from late 2010 to October 2015. The redesigned Mojang cape then covered staff until July 2021. Both are Java Edition capes, and neither was given out on Bedrock Edition.