AWS- cloudformation "import existing resource" is giving an error

Question

I'm new to cloudformation- I have manual created EC2 instance2 and another EC2 instance1 using cloudformation sample yaml file. I want to add the manually created instance2 using "import existing resource" option.

but i'm getting below error-

You have modified resources [MyInstance] in your template that are not being imported. Update, create or delete operations cannot be executed during import operations.

below is the yaml file

AWSTemplateFormatVersion: "2010-09-09"
Metadata:
    Generator: "former2"
Description: ""
Resources:
    EC2Instance:
        Type: "AWS::EC2::Instance"
        Properties:
            ImageId: "ami-0742b4e673072006f"
            InstanceType: "t2.micro"
            AvailabilityZone: !GetAtt EC2Instance2.AvailabilityZone
            Tenancy: "default"
            SubnetId: "subnet-09ec4c74f9226b0a5"
            EbsOptimized: false
            SecurityGroupIds:
              - "sg-0ba5c892cb4456045"
            SourceDestCheck: true
            BlockDeviceMappings:
              -
                DeviceName: "/dev/xvda"
                Ebs:
                    Encrypted: false
                    VolumeSize: 8
                    SnapshotId: "snap-097c45e6d3c6e0d1b"
                    VolumeType: "gp2"
                    DeleteOnTermination: true
            HibernationOptions:
                Configured: false
            EnclaveOptions:
                Enabled: false

    EC2Instance2:
        Type: "AWS::EC2::Instance"
        DeletionPolicy: "Retain"
        Properties:
            ImageId: "ami-05fa00d4c63e32076"
            InstanceType: "t2.micro"
            KeyName: "ThisIsTestKeyPair"
            AvailabilityZone: !Sub "${AWS::Region}a"
            Tenancy: "default"
            SubnetId: "subnet-09ec4c74f9226b0a5"
            EbsOptimized: false
            SecurityGroupIds:
              - "sg-0847c55c903c6b01d"
            SourceDestCheck: true
            BlockDeviceMappings:
              -
                DeviceName: "/dev/xvda"
                Ebs:
                    Encrypted: false
                    VolumeSize: 8
                    SnapshotId: "snap-0834d7afbcb68e0b7"
                    VolumeType: "gp2"
                    DeleteOnTermination: true
            Tags:
              -
                Key: "Name"
                Value: "EC-manual-for-CF-testing"
            HibernationOptions:
                Configured: false
            EnclaveOptions:
                Enabled: false

Answer 1

If you are using SAML or any other transformer, CloudFormation won't let you import new resources. https://repost.aws/knowledge-center/cloudformation-template-resources-error

Answer 2

You can't create/updated resources in CFN at the same time as you import other resources. You have to do it one, by one:

1. Remove EC2Instance2 from your template and deploy EC2Instance
2. Add EC2Instance and import the second instance.