Hello, my name is XXXXX XXXXX it is my pleasure to assist you with your question today.
I cannot think of a specific reason your employer has not followed the correct procedure - it could be a simple case of them overlooking the rules and managing this situation inappropriately. It does not necessarily mean that this was done on purpose and with the aim of denying you redeployment opportunities. If you have a specific policy which states this step should have followed the interview process, by all means remind your employer of this and ask for clarification as to why it was not followed in your case - you have every right to know.
In terms of VR, this is not a right, it is simply an option which can be exercised at the employer's discretion. There is no obligation on an employer to offer VR to its employees but that could be an option in order to reduce its workforce with volunteers rather than by going though the full redundancy procedure and select employees that way.
When it comes to the job you were offered, if this is a demotion and results in lower pay you do not actually have to accept it. The employer has a duty to offer you suitable alternative employment, however if the position they have offered you is not suitable then you can reject it and opt for redundancy instead, or another suitable alternative, if one exists.