@someguy_1990
There is one important point; you cannot amend your previous returns.
Since you did not take any depreciation deduction in the first year and then failed to do so without correcting that error in a tax return for the following year, you adopted an impermissible method of accounting and must file Form 3115 and make a Section 481(a) adjustment. You will almost certainly need professional assistance with this matter.
See Treas. Reg, §1.446–1(e)(2)(ii)(d)(2)
See also https://www.irs.gov/publications/p946#en_US_2018_publink1000107386
