Yes. You can verify mark sheet or other documents (like degree certificate) issued by EIILM University through RTI.
As EIILM University has stopped functioning, the RTI application should be addressed to the designated PIO under Department of HRD, Government of Sikkim. RTI applications addressed to Sikkim should be accompanied by a copy of any of Government ID proof (like DL, PAN Card, Aadhar Card, Passport etc.) of the applicant.