= Solution
<protonation> activates the <oxygen> of the anomeric <acetal> bridge. Cleavage of its bond to the <anomeric carbon> releases that tether <oxygen> as the terminal primary <alcohol>, while the other ring <oxygen> stabilizes the developing anomeric <electrophile> by <lone pair> donation. The resulting <oxocarbenium> description has a nearly planar reactive anomeric centre; it need not be drawn as a long-lived free <carbocation>.
<methanol> attacks that centre, giving a protonated methyl <acetal>, and <deprotonation> regenerates <acid (chemistry)>. \b[The former bridge becomes CH2OH; the anomeric <substituent> becomes OMe.] The other C–O bonds and existing <carbon> configurations are retained. The ring can adopt a different chair once the bridge constraint is removed, so an apparent movement of <substituents> in the projection does not imply inversion at all the other <carbons>.
The depicted anomeric OMe is axial in the product chair. This geometry allows an endocyclic <oxygen> <lone pair> to align antiperiplanar to the exocyclic C–OMe bond, providing $n_O\rightarrow\sigma^*_{C-O}$ stabilization associated with the <anomeric effect>. Acidic conditions also permit cleavage and recapture at the anomeric centre, so selection is not simply backside displacement at an unchanged tetrahedral starting <carbon>. The <anomeric effect> rationalizes the specified axial product; the scheme alone gives neither its numerical equilibrium population nor evidence that every other <anomer> is absent.
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