You can use singularity python functions to check your manifest. First download it
git clone -b development https://www.github.com/singularityware/singularity.git
cd singularity/libexec/python
From the singularity/libexec/python folder do:
ipython
from docker.api import *
client = DockerApiConnection(image="poldracklab/fmriprep:0.4.4")
manifest = client.get_manifest()
# Then look at the version
manifest['schemaVersion']
# if you want to force version 1.0
manifest = client.get_manifest(old_version=True)