The Himalayas formed from the crumpling of two continental plates when India slammed into Eurasia. In this kind of collision, the result is upward crumpling. So the Himalayas is still growing while India is shrinking (stop cheering Pakistan!)
I don’t know of any similar observed case but a good bet might be the Mediterranean area where plates have been known to slam into each other and then separate. But there are no impressively high peaks there.
Tall mountains that form by the collision of oceanic and continental plates (like Andes) are almost always volcanic. They’re not very tall. Mt Aconcagua is an exception. Most volcanic mountains erode very quickly (in geologic terms.) But Aconcagua stopped being a volcano and became the victim of crumpling between the oceanic plate (Nazca) and the south American shield (continent) so it’s a hybrid volcanic arc - and result of crumpling (thrust faulting.)
Your other question, ancient tall mountains? The present is the key to the past, so there was likely a mountain similar to Everest (in type of formation if not height) that has either eroded down or was faulted down.
The entire Himalayas is growing as mentioned above but I don’t think any other peak is chasing Everest, except maybe K-2.