No they did NOT have DOLBY from early on. the first cassettes had no Dolby B, no CRo2 tape, and inferior tape heads. they were basically made for dictation and such, not HiFi. early units were mono only. Eventually, they evolved where the 8T did not. When things like Dolby B and CRo2 tape first came out, they were on high end very expensive machines. eventually, things like DBX, and Dolby pro were added to the mix.
A bastardized version of the 8t existed for years after the death of the 8t in the NAB cart they used in the broadcast industry. These carts had a big hole where a external pinch roller was inserted into the cartridge, vs the 8T's internal smaller pinch roller
bob