The first question was answered well by Brythan, so I will answer the second.
Today, is the constitution stored digitally so that any new revisions can be made with ease?
No. There is no Master copy of the constitution, and even if they were all blown up, the constitution would not change.
So first, there is not physical or digital Master document that, when changed, changes the constitution. The constitution changes precisely once the amendment is ratified by 3/4ths of the states (this would now be 38/50). The Archivist of the United States, who is in charge of the National Archives and Records Administration, certifies that this has been done and signs a certification. As user
According to 1 USC 106b, the Archivist must publish the amendment, along with the certification, which serves as the formal legal notification that the amendment is now a valid part of the constitution. This is done in the Federal Register.