Actually, Chris Latta died before he could reprise his role as Starscream, so Starscream was done by Doug Parker aka Terrasaur who claims he was actually good friends with Chris, & was taught how to talk like Starscream. Though, I never thought he did a perfect job, but, he was decent. I feel he really wasn't good at all at doing Starscream at a level tone, but, did good with Starscream's screaming voice.
As for Dinobot, it was just a dumb generic name, like Rhinox, Insecticon(toy only), Tarantulas, Tigertron, & Iguanus(toy only). He didn't have any connection to the Dinobots. If anything, he might've taken the name, because he respected the Dinobots for being warriors, but even then, he was born the spark of a warrior/Predacon, rather then a worker/Maximal(going by G1 standards that is).
Also, Ravage & G1 Megatron were also in the show, though, G1 Megs was not voiced by Frank Welker(by this time, Frank was a very expensive man to hire). Plus, really, most companies don't bother to get the same cast several years later, when a show continues. Look at The New Adventures of He-man, which is a continuation storywise, but has none of the original actors. In Japan, that's a different story, they always try to make sure to get the same actor's, no matter how many years it's been.
Oh, also of note, G1 Megatron was a gun. Beast Wars Megatron, had no relation to G1 Megatron, he only took the name in respect of the original Decepticon leader. But, IIRC, there might've been some kind of connection between Prime & Primal, though, neither was the same guy. Basically, they might be related somehow, just like Prime & Ultra Magnus. Since the show happens in the future, the original Optimus & Megs are long dead, well, atleast Optimus for sure. Megs, they aren't as vocal about. For all we know, he could be still floating around out of control in space(as Galvatron) which happened at the end of the Rebirth episodes of G1.
