If employees are working hard for a whole year under one leadership and suddenly leadership changes, who shall rate year end performance,new or old boss?

There are many ways to rate your performance. If you have a history of achieving higher target goal then there must be a record of your activity on system. In some cases your old leader may write down a report based on employers performance as per required by new leader. If you already have a record available regarding your performance in that case yes the new leader will notice it based on your previous records and achievements. Mostly when there are reports on sales or operations, each activity is recorded with the concern parties involved in any particular business activity.

New boss with discussion and ordination with the old boss.

its should be Old boos with attending the new boss , new boss should review q1,q2,q3

old boss need to give details for the new boss , new boss need to write his feedback of the performance 

It is always the boss in charge at the time of evaluation of staff. However, criteria to evaluate should come from HQ.

If employee is working hard and his expertise is the key role in the growth of the organization/company. So the company Higher management must observe his/her each activities which is done for the organization and make the report on the basis of his/her performance. If the boss changes suddenly so employee historical performance report should be handed over him. so the new boss rate the employee performance on the basis of previous performance report and his own judgement. And the latest way to call that employee for interview and give him a few minutes task according to his/her job and see how they will perform.

Ths needs to be addressed from governance perspective which means the organisation policy should have defined process around this.  Many professional organisations does have policy of asking both the leaders to review if the individuals had worked for closed to 6 months under both the leadership.  The critical aspect is to take the right stand during ambiguity of any leadership gap so the morale of the employee is maintained.  

NEW BOSS GIVES U THE YEAR PEEFOMANCE

no matter who is boss ,work is work ,if you are doing job you should be able to perform all duties under hoesty and work with piety. 

It should be the old boss as he was the one to share the workign experience and can therefore review the performance of the employee.

The new boss will be the final evaluator, the predecessor is the co-evaluator. Thus, the opinion is 50:50