The AWS ACM public certificate is free, you only pay for the AWS resource that is using the certificate, for example Load Balancer.
The AWS ACM Private CA is not free. You have to pay for the private CA operation and also certificate issued.
Yes ACM is a regional service. You have to create a certificate on each region where you plan to use it for your AWS resources.
You cannot use AWS ACM public certificate in EC2 instance since you cannot export the certificate.
You can use AWS ACM private certificate issued by AWS ACM Private CA by exporting the certificate and use it on your EC2 instance.
ACM periodically validate the DNS records.
Yes. You don’t have to use AWS Route 53 domains to be able to use AWS ACM certificate. After creating the ACM certificate you have to create DNS record for validation on your provider so ACM can continue issuing the certificate.
AWS ACM in North Virginia (us-east-1) doesn’t affect regional resource but it affect and needed by global resource like AWS Cloudfront.
ACM is regional service. You have to create ACM certificate on each region.
Create a CNAME record as instructed by AWS ACM.
The validity of and AWS ACM certificate is 13 months (395 days)
We cannot download ACM public certificate so we cannot install ACM certificate to EC2 instance.
No, you don’t need to add trailing period for name and value.
You can put ALB / ELB in front of EC2 instances hosting your WordPress and use the AWS ACM on the ALB / ELB.
As alternative, you can also use AWS ACM private certificate, export the certificate and use it on the web server on your EC2 instance that is hosting your WordPress.