If you can get on to one of these cadet programmes I think you would be doing very well for yourself. However it would be better getting information from somebody who is already on one. My understanding is that some of the cadets are spending a significant amount of time waiting for training slots to be made available. On the one hand they are being paid, on the other it can be very frustrating.
Be very wary about the word "Guarantee!" Few things in life are, and there are simply too many variables and unknowns for any job to be guaranteed.
As with all of these programmes, there is certain to be a great deal of competition for a few places. The choice of candidates falls to the airlines concerned from the applications received.
Have you made an application?