You have three years from the due date of the tax return to file for a refund. So you must file a 2015 return no later than April 15, 2019, to claim the refund. You can find prior year tax forms from the IRS at https://www.irs.gov/forms-pubs/prior-year.
For 2007, a high deductible health plan is a health plan with an annual deductible that is not less than $1,100 for self-only coverage or $2,200 for family coverage, and with annual out-of-pocket expenses that do not exceed $5,600 or $11,200, respectively.