No, you have to file a separate tax return for each year. You cannot combine them.
You cannot use TurboTax Online to file for 2019. TurboTax Online is only for the current tax year, which is now 2020. To file for 2019 you have to use the CD or download TurboTax software for 2019. You can purchase a download at the following link. There is no free filing for past years.
You might get a better price from a reputable online seller that still has TurboTax for 2019 in stock.
Tax returns for past years cannot be e-filed. You will have to print your 2019 tax return, sign it, and file it by mail.