How to regenerate a plant after harvest?

So assuming that youve cut half the plant with buds could you put this plant back into vegg.

Yeh, you could. Just flush, if it hasn't been flushed already, feed some veg nutes and put it back on 18/6.
It can take a while re-vegging, it really is much quicker cloning before flower, or growing another from seed.
I got bored waiting the only time I tried...