I cant access my 2017 taxes because I accidentally started the 2018....can you delete the 2018 out to access the 2017?

You can access the prior year from the program you are using now ... you just need to pay for it now instead of later when you file.   If you want to clear and start over from the FREE version you can upgrade to PLUS you can if you have not registered the account yet ...

If you would like to erase the data you have entered, you can do that by following these directions:

1.     While in your TurboTax Online program (after clicking Continue your return)
   Select tools.
2.     Then click on Clear & start over.
3.     On the Are you sure you want to clear your return? pop up screen, if you are sure about clearing all your entries and starting over, click Yes.
4.     Then a new screen confirms you have cleared your entries, click Continue.

All of your entries will now be erased and you can start over in the FREE version.

How do I pay for PLUS in TurboTax Online?

https://ttlc.intuit.com/community/payments/help/how-do-i-pay-for-plus-in-turbotax-online/00/27001