Gavotte No. 1 is written in g minor with no structural phenomena other than the double bar lines dividing sections A and B. The piece is written in g minor – there are no marked changes in key signature.
The A section encompasses measures 1 through 8, and is repeated. This section is a parallel, symmetric period, with the antecedent phrase ending in the middle of measure four on an IAC, and the consequent phrase ending on a PAC in measure 8, tonicizing the relative major key, Bb Major. I would consider the A section open or continuous, in that it modulates to Bb Major. The A section is expository.
The B section appears to tonicize d minor right away, evidence of structural division that is not obvious at first glance. The B section is a phrase group that is repeated, and is definitely tonally unstable. It expands upon themes from the A section, so it must be developmental. There is a PAC in d minor at measure 18. There is a cadence at measure 26 that is a little more ambiguous to me, since it occurs so quickly. It seems to be a HC in g minor, meaning that we’ve returned to the tonic key. The final cadence is, of course, a PAC in g minor.