By Practicing or Practising?

In Australian and British English, 'practise' is the verb and 'practice' is the noun. In American English, 'practice' is both the verb and the noun.

Is it Practising or practicing UK?

If you use British English, you'll need both practice and practise, so you've got a bit more work to do here. In short: you should use practise when you're using the verb (that is, the 'doing' word), and practice for the noun (or 'thing' word).

Is there a word practicing?

It means “to do something repeatedly in order to master it” or “to pursue as an occupation or art.” So a churchgoer can practice their religion, just as a student might practice the violin. In British English, the verb form of the word is rendered as practise.