Yes...well...back to the actual point of this thread...
No, Tenshinhan was in no way stronger than Cell or the Androids at any time ever. The technique he used to push back Cell, the Shin Kikoha, is an attack that literally takes all of his life force and throws it at the target all at once. The result is a blast that is several thousand times stronger than anything Ten would ever be able to manage otherwise.
The Shin Kikoha isn't used too often because overusing it literally kills the person performing it...it uses up that much of his life force. When Ten dide in the Saya-jin saga, it wasn't because of anything Napa did to him. He died because he literally put every ounce of his ki into his blast...and it killed him.
If you'll notice, Ten didn't actually do any damage to Cell at all. All he did was push Cell back and annoy him.
...and both Tenshinhan and Kuririn are humans. There is absolutly no doubt in this area. So Ten has a third eye. So Kuririn has no nose. So what? This is a world where cats and dogs live like normal people, dinosaurs still inhabit the wild, and entire buildings can pop into a lil pill bottle. Nobody in the series truely looks like a "normal human", even the normal humans.
...oh and BTW, Piccolo was the first to know how to fly, but Tenshinhan was the first character we see fly.