A Provisional ball, as described, is ALWAYS classed as '3 off the Tee' - provisionally! You must announce it as a 'provisional ball', otherwise it isn't provisional, so becomes the ball in play (and 3 off the tee).

Is a provisional shot 2 or 3?

It is one stroke. Just one. But do note that you also get a penalty of stroke and distance with it. And there may be special cases wherein you could hit a provisional ball more than once – a scenario which is also covered by one of the questions answered here.

What happens if you lose your ball off the tee?

When you have lost your ball, or hit a shot out of bounds, which is marked by white stakes or lines, the penalty is one stroke and distance. What this means is that you incur a one-stroke penalty and need to go back to the point from where you hit your last shot.