A few things here to clarify for you.
Your employment contract is not just one thing - it is a combination of written particulars, terms detailed in a company handbook or in plicies available for employee to read, custom and practice.
Your Job Title (and maybe a BRIEF description) is part of your contract, but that doesn't mean the employer can't change it. Whether or not the change proposed is fundamental enough, I can't judge. I hope that you are not trying to use a detailed job description to decide what you will or won't do.
Training comprises many aspects - formal training, on-the-job experience, coaching from LManager or others.
What is your bonus proposed to be based on? - it can't be what you say - it must be a measurable target of some sort. And what was was your previous bonus based upon and is it contractual (in a letter to you?)
What equipments are we talking here - safety equipment, computer, technical kit?