The mitzva of shmita is in essence divided into two parts.
2. The second part deals with "ושבתה הארץ שבת לה'" Vayikra, 25:2 (the land shall observe a Shabbos of Hashem) Here the mitzva is to refrain from work in this time. This can only be attained with land that was worked in the sixth year, and then left fallow in the seventh.
The psak of HaGaon Rav Elyashiv pertaining to mechiras chametz and a heter iska was that the documents should all be legally acceptable and that one should not be able to void them in court. Same is with the din for kinyanim in halacha regarding ownership of land: In order for the kinyan to be complete, one must ensure the legalities are in order as well.
When dealing with ILA, you’re obtaining a long term lease, not complete ownership.
When it comes to ILA residential lands, there might be a way to consider it buying rather than leasing, yet an agricultural land, such as this, is considered on a "lower level" for 3 main reasons:
No. Being that renting is not koneh, the field remains in the owner’s possession and doesn’t belong to the renter. It also works the other way around: If a yid rents his land to a goy, he still needs to do the mitzva of shmita because the land belongs to him.