• Can I buy wine made from shmitah produce?

• Is heter mechirah valid?

• Can I buy an esrog grown during shmitah?

• Can I buy produce grown in Israel during shmitah?

Attached Visuals:

The Effect of Mistakenly Eating Foods in which Shmitah Applies, and its Remedy

In an answer to a specific family that was suffering from a medical issue, the Rebbe responded:

בטח שגגו באכילת דעניני שמיטה.
(They transgressed unintentionally, by eating food to which Shmitah applies).

When they received the answer, they asked how to start checking into this,
as they are generally careful to only buy products with Mehudar Hechsherim.
The Rebbe responded:

עבודת ה ' בשמחה (שפורצת גם גדר דשגיאות מי יבין).
(Serving Hashem with joy (which breaks also the boundary of unintentional transgressions).

-ליקוטי שיחות חלק ל"ו, ע' 298
(Likkutei Sichos, Volume 36, Page 298)