How to extract keys from multiple, nested arrays using jq

SETUP

I'm trying to figure out how jq filters work and having trouble figuring out nested arrays. Using the data below I cannot make a flat 5 key output. I can get 1 key and 4 nulls or 4 keys and 1 null, but not all 5 keys.

1 key, 4 nulls:

.Reservations[] | {OwnerId, InstanceId, ImageId, PrivateIpAddress, Platform}

Returns:

{
 "OwnerId": "000000000000",
 "InstanceId": null,
 "ImageId": null,
 "PrivateIpAddress": null,
 "Platform": null
}

4 keys, 1 null:

.Reservations[].Instances[] | {OwnerId, InstanceId, ImageId, PrivateIpAddress, Platform}

{
  "OwnerId": null,
  "InstanceId": "i-v33333333",
  "ImageId": "ami-44444444",
  "PrivateIpAddress": "10.0.0.0",
  "Platform": "windows"
}

For a various reasons I cannot use the "--query" option in AWS CLI which does return the format I'm looking for:

aws ec2 describe-instances --region us-east-1 --profile temp --query 'Reservations[*].{InstanceId:Instances[0].InstanceId,IP:Instances[0].PrivateIpAddress,Platform:Instances[0].Platform,OwnerId:OwnerId}'

Output:

[
    {
        "InstanceId": "i-11111111",
        "IP": "10.9.9.3",
        "OwnerId": "111111111111",
        "Platform": windows
    },
    {
        "InstanceId": "i-22222222",
        "IP": "10.0.0.0",
        "OwnerId": "111111111111",
        "Platform": windows
    }
]

Here is the JSON input:

   {
    "Reservations": [
        {
            "OwnerId": "000000000000",
            "ReservationId": "r-22222222",
            "Groups": [],
            "RequesterId": "111111111111",
            "Instances": [
                {
                    "Monitoring": {
                        "State": "enabled"
                    },
                    "PublicDnsName": null,
                    "State": {
                        "Code": 16,
                        "Name": "running"
                    },
                    "EbsOptimized": false,
                    "LaunchTime": "2015-04-10T00:02:02.000Z",
                    "Platform": "windows",
                    "PrivateIpAddress": "10.0.0.0",
                    "ProductCodes": [
                        {
                            "ProductCodeId": "0000000000000000000000000",
                            "ProductCodeType": "marketplace"
                        }
                    ],
                    "VpcId": "vpc-2222222",
                    "StateTransitionReason": null,
                    "InstanceId": "i-v33333333",
                    "ImageId": "ami-44444444",
                    "PrivateDnsName": "ip-10-0-0-0.aws.foobarcloud.com",
                    "KeyName": "bar-servicemesh",
                    "SecurityGroups": [
                        {
                            "GroupName": "bar-wildcard-dns-intranet-InstanceSecurityGroup-VN0DFQ13QCDY",
                            "GroupId": "sg-55555555"
                        }
                    ],
                    "ClientToken": "11111111-2222-3333-4444-555555555555_subnet-66666666_1",
                    "SubnetId": "subnet-66666666",
                    "InstanceType": "t2.medium",
                    "NetworkInterfaces": [
                        {
                            "Status": "in-use",
                            "MacAddress": "00:00:00:00:00:77",
                            "SourceDestCheck": true,
                            "VpcId": "vpc-66666666",
                            "Description": null,
                            "NetworkInterfaceId": "eni-11111111"
                        }
                    ]
                }
            ]
        }
    ]
}

QUESTION Using the JSON input above, how do you use jq to produce the following output?:

{
  "OwnerId": "000000000000",
  "InstanceId": "i-v33333333",
  "ImageId": "ami-44444444",
  "PrivateIpAddress": "10.0.0.0",
  "Platform": "windows"
}