Is it possible for users with a Platform license to access the Standard
Well yes and no,
In Standard Salesforce UI, no. You cannot even assign Order CRUD via permission SET.
In VF, APEX, Aura, LWC Yes. You have to use custom apex classes, triggers, and wrappers and get your job done. Its because Apex runs in System Mode and surpasses license limitations.
Should you do it? Doing this breaks the Master Subscription Agreement. If salesforce finds this out you have to pay for the full Salesforce License as this comes under license abuse.
Someone managed to CRUD on opportunites using Chatter free license. See God mode abuse.
Edit: As Requested breaking contractual limit clause is under Usage limits Section 3.2
Services and Content are subject to usage limits specified in Order Forms and Documentation. If Customer exceeds a contractual usage limit, SFDC may work with Customer to seek to reduce Customer’s usage so that it conforms to that limit. If, notwithstanding SFDC’s efforts, Customer is unable or unwilling to abide by a contractual usage limit, Customer will execute an Order Form for additional quantities of the applicable Services or Content promptly upon SFDC’s request, and/or pay any invoice for excess usage in accordance with the “Invoicing and Payment” section below