If the employer issues a W-2 for the paychecks you received for the new job, you must include it on your 2024 tax return. The returns that folks are working on now are not 2025 returns----they are 2024 returns for the tax year that just ended. Any income you received in 2024 must be included on your 2024 tax return. The employer has until January 31 to issue W-2's. If you began working there late in December, it is possible that you did not get a first paycheck until January----ask the employer if they will be giving you a 2024 W-2.
It depends. If you were not actually paid until January, 2025, then your income will be included with your W-2 for 2025. If this is the case there is nothing to report for 2024.
If you did receive a paycheck that was dated in 2024, then you should wait for the W-2 to be issued to you from your new employer.