Monthly Payments on the Increased Child Tax Credit - Can I skip them?

My wife and I file jointly and get the child tax credit for our kids each year.

I understand that the latest stimulus bill increased the CTC to $3600 or $3000 per child (depending on the child's age) and that it created a provision for the IRS to send out monthly payments as an advance on the anticipated credit.

Question 1: is the increased amount ONLY for tax year 2021 or is it for future years? (I'm seeing conflicting info in the articles I've found).

Question 2: Is there an option to skip the monthly payments and just get the credit next year when I file my 2021 tax return? If so is there anything I need to do to opt out of the monthly payments?

I know its "better" to get your money sooner, but the money would just sit in a savings account at 0.05% interest anyway so I'd rather just get it all at once.