Your TurboTax Online account maintains only one version of a tax return. You may only e-file one tax return.
You may create one version as a Single taxpayer and print it out. You may create a second version as a Head of Household taxpayer and print it out. You may add and delete dependents but each time you should print out the results so you have something compare to the other versions.
The CD/Download version of Turbotax will prepare as many Federal tax returns as you would like. Only five tax returns may be e-filed.
See this TurboTax Help.