Thank you for your question. Using your numbering:-
1) No, your employer must give you notice when they dismiss you, they are only allowed to dismiss you if they summarily dismiss you. This happens when an employee commits a repudiatory (very serious) breach of contract. (eg. gross misconduct, theft from employer, revealing trade secrets, gross negligence). Upon dismissal they will either make you work your notice period or offer to pay you in lieu of that notice period
2) It is sensible for you to attend this and certainly if you are intending to make a claim against your employer (how long have you been employed at the company?) for unfair dismissal or wrongful dismissal (which depends on how long you have been employed). You are not obliged but if you do not attend it may prejudice any future claim you issue against them. You can choose to be accompanied to every meeting under in the procedure.
You can resign if you wish, but it does not really give you any advantage unless you simply "want out" of the job and the hassle of the disciplinary procedure. The employer must be fair throughout the disciplinary procedure so I should have thought it would be worth you attending, if they are not fair this will impact badly against them in the event that you were to bring a claim against them. You will have to give the notice period under your contract.
3 Your employer can refuse to give a reference, the give a reference they are under a duty to provide an accurate one which does not mislead the prospective employer. In all likelihood they will want to avoid speaking about the disciplinary process - if it is misleading it could amount to defamation in which case you could claim for libel
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