Car. 746 questions in 14 topics.
Three routes through the same bank, each one chosen from what you have actually answered rather than from where you last stopped.
A mock is the DVSA format end to end, marked at the end and never during. Everything you finish is kept exactly as it was on the day.
Every question in all four is free. Your answers are kept per licence, so switching to look at another one and back again loses nothing.