Do you get your renewed passport the same day you renewed or do you have to come back in person for it? Can it be mailed to your address?

You do not get the passport the same day. In some cases if there is an emergent need, you can get it after speaking with the immigration officer if available. They usually give you a date for pick up, they also have an option to mail it to you but there is a fee of $30(not 💯% sure on the price) to mail it to you. You can also sign a consent letter with your original passport attached and give to someone to pick up for u.

The earliest biometric interview dates are in April 2022 for passport renewal. Please how can one get an expedited date earlier than that? Are there people to contact?

If you do not wish to pay the $30shipping fee at the embassy, then go with your prepaid certified priority mail envelope and submit this to them during your appointment. Your passport will be mailed back to you when it is ready. Note that the mail must be certified.